The Lighting Time Table

To read the entire tutorial, you can just click on the first link and then continue to the next section at the bottom of each page. Or, you can select links below of interest to you.

PRE 1900 SECTION

Overcoming Obstacles
About Early Electric Lighting, Generators, Arc Lamps, The First Edison Socket, Menlo Park, etc.
The First Fixtures
About The Start Of The First Incandescent Lighting Fixtures
Light Reflection
About Early Light Bulbs And Candle Power vs. WATTS
Edison-Bergmann
About Sigmund Bergmann And The Start Of Bergmann And Company Lighting Fixtures
Lighting Break Down
A Quick Break Down Of Different Lighting Time Periods
Styles 1881 to 1884
Bergmann Fixtures And Styles
Other Pre-1888 Styles
About Early Companies That Sold Lighting Systems And The Fixtures That They Sold With Their Lighting Systems
The U.S. Elect. Co.
The United States Electric Company History And Early Items
The Brush Elect. Co.
The Brush Electric Company History And Early Items
Thomson-Houston
The Thomson-Houston Electric Company History And Early Items
Westinghouse
About The Westinghouse Manufacturing Company History And Early Mergers
Mid 1880's Styles
About The Start Of Electrical Supply Houses and how new lighting styles came about
Pre 1900 Sockets
About Early Light Sockets And How To Tell The Difference
1887 New Items
1888 New Items
1890 New Items
1891 New Items
1892 New Items
1893 New Items
1894-1896 Items
1897 New Items
1898 New Items
1899 New Items
Above are catalog items sold in different years. There is no space to duplicate items, so only new and unique items from each year are shown. You would need to view the catalogs for yourself to be complete as I am only highlighting items. You can view catalogs here.

EXTRA INFO
Victor Shade Holder
About The Victor Shade Holder, Atwood And The Standard Holder

I.P. Frink 1899 Items
About Frink & Wheeler
New Wheeler Inverted
Three Links About Mirror Reflector Manufacturers And Their Items And History.
Wheeler Reflector Co.
NEW - A history of The Wheeler Reflector Company and tips on how to tell if mirror has been replaced on a shade

Early Desk Lamps
Some Help In Telling Them Apart

Vitrite And Luminoid
About The Vitrite Holders And Early Vitrite History

Brush-Swan Holder
About Brush-Swan Shade Holders

Cord Balls
My cord pendant adjuster project, as well as a good history about them.

POST 1900 SECTION

About 1900 Styles
This section covers a basic into into the 1900 section covering information about the 1899 transition, electrical code changes, lighting influence, sharing and licensing of patents and then into the new section of electrical specialty manufacturers,

Electrical Specialty Manufacturers
Harvey Hubbell
This section covers some early history periods of pre Hubbell-Grier, Hubbell-Grier, Harvey Hubbell, Hubbell Company. It also covers a number of items that helped change lighting styles,

Benjamin
This section covers some early history periods for the Benjamin Electric MFG. Co, as well as a small section on Dale and The Federal Electric Company
Dale
Federal Electric

This post 1900 section continues to be under current construction

Please Check Back.

ABOUT THE LINEUP

The No. 3 Bergmann socket is part of a lineup. A socket line up simply means that a socket design was carried through different mergers or sister companies, as well as different periods of time. In this case starting as an Edison/Bergmann invention and then living on through later company mergers.

The lineup shown below is for the Bergmann moving tongue socket.

Please check back from time to time for updates to this section. If a future update is ever added to this page, it will be added in the format of a red dated headline to make it easy to find.

Since the No. 3 socket design extended through many years, we will cover the entire lineup of moving tongue sockets and then move on to the Bergmann No. 4 socket, which would be the next oldest socket after the first moving tongue.



As you can see from the lineup examples shown above, not too much can be seen from one simple group picture of the out side of these sockets. While there are a number of differences on the out side that will be pointed out, the lineup will also consist of changes to the socket innards, different patent dates added missing or misprinted on the shells, as well as many more changes that help to ID sockets from different time periods.

Before getting into each different moving tongue socket, we should go over some general knowledge information that will help you to understand each different socket in the lineup more clearly.

ABOUT THE SOCKET

The moving tongue was the second "turn key" socket invented by Bergmann.

The turn key is simply the off and on switch, which was also called a cock in the old days.

The first socket with a switch was the Bergmann No. 1; The Bergmann No. 2 (socket lineup), was the acorn socket(s) which never had a turn key or switch on them.

There were several reasons why Edison and Bergmann needed to upgrade or re invent the older (no. 1) key socket.

PROBLEMS WITH THE FIRST WOODEN SOCKET INNARDS
This first Bergmann key socket was made with wooden innards, which would swell in moisture and sometimes cause the thin brass shell to crack. Also as the wood swelled, you could no longer take the socket apart now being like a cork in a bottle.

Another downfall was that these older wooden innards needed to be hand carved, filed, sanded, etc., which was a lot of work to produce in mass quantity. The real goal was to find a better and easier material to work with, that did not require much time or effort to manufacture.

I can document many orders for these sockets.

One would think that for such an early time in history, that there was only a small number of sockets being manufactured.

WRONG! - I started calling special attention to this fact as I came across more and more orders during my research.

While there were orders for 100 and 200 every now and then, most of the orders that I came across started at 500 sockets! There was also the occasional order for over 1000 sockets at once, as seen in the telegram sent to Bergmann from Samuel Insull shown above on your right which says "Have order for three thousand sockets with cocks for Europe". Insull was then asking if they could be shipped from their company in London, so as not to over ship by fulfilling the order and shipping from the U.S. to Europe.

My point is, that with all of the growing interest in incandescent lighting at the time - There was not just a small need to upgrade the old style wooden socket - There was a big one!

THE SEARCH FOR A NEW MATERIAL
The largest problem during this time was the material that was to be used in the place of wood.

Many different compositions and insulating materials were tested before this socket was invented.
Even though the moving tongue socket was not applied for patent until April 10th 1884, most of the material testing was already complete and documented in the Menlo Park Notebook No. 143 which covered the time periods from December 2 1882 and March of 1883. Note worthy is the fact that some of the compositions and different formula combinations tested were used on later moving tongue sockets, as well as other items such as switch bases.

The main reason for the tests and experiments found in this notebook, was to find or invent a good composition material (for the use of sockets and lamp bases). Most importantly this composition 'cement' was to be a direct replacement for wood as an insulating material for lamp bases, socket innards, safety fuses, etc.. Wooden socket collars during this time, were replaced with hard rubber and different wood fiber based compositions.

On December 28th 1882 (while this testing was still well underway), Edison sent samples along with a letter to Charles Batchelor.

He stated in his letter "I have just got a new compound that I think will be good for sockets of lamps". He asked that Batchelor test the compound himself and report back. Edison was clear about the reason for this testing when he stated:

"Bergmann is going to experiment with the compound to see if he cannot mould the sockets thus displacing wood"

Also in the notebook, after each variant of different composition mixtures it states "made socket" (meaning lamp base) and then it was tested to see how it held up to different tests.

Even though I can document several changes and updates to the first Bergmann turn key socket, there is no evidence that this socket ever used anything other then wood for it's cylindrical block (shown as "A" in the patent). The "disk" lower case "h" was likely upgraded from wood to vulcanized fiber as evident from the pictures shown of it on this site.

For someone wishing to read and learn more about defects in early Edison items (that needed to be fixed or upgraded), you can study through the 1882 (broken link) and 1883 (broken link) Edison defect books. (Note that the defect books were downloaded from the Edison papers project at rutgers.edu, and converted to PDF for easy viewing for the readers on this site).

THE MOVING TONGUE WAS THE FIRST EDISON / BERGMANN TURN KEY SOCKET MADE WITHOUT USING WOOD

The moving tongue was the first turn key socket made without using wood for any part.

The moving tongue ingeniously used a brass frame (called the skeleton), that replaced the wooden cylindrical block of the first socket design.

The moving tongue then used what was called the "insulated disk", which was mounted to the skeleton and provided the insulated environment (or starting place) to connect to both isolated positive and negative terminals.

Bergmann's search for the best insulating material (to be used for the socket's insulated disk), is what will cause many changes as we go through the first several sockets in this lineup.

THE MOVING TONGUE - A SIMPLE CONCEPT
When you turn the key on the socket, the key moves inwardly and pushes the tongue (center contact) forward (upwardly). The picture on the right shows the switch in the off position. If you can picture a bulb screwed in the socket, you will see that the tongue in this position would not be touching the center contact of the bulb.

However, as you can see from the second picture on your right (shown with the key in the on position), when the key is turned and the tongue moves forward (upwardly), it is then forced to touch the bulb's center contact (which makes the electrical connection).

TIME FRAMES
This moving tongue socket was sold and used by Bergmann & Company (Edison & Bergmann) from 1884 until 1889. It was then sold by the Edison General Electric Co. (Edison Only) from 1889 until 1892.

THE DIFFERENCE BETWEEN BERGMANN & E.G.E MOVING TONGUE SOCKETS
Moving tongue sockets made by Bergmann & Co., are mostly found with red gelatinized fiber innards like those shown here on your right (I will cover other early materials used on moving tongue sockets below). Those made by Edison General Electric are most always made from porcelain. There are some that were made by E.G.E (right after the merger in 1889 and until the first part of 1890) that were made of red gelatinized fiber (but rare to come by). These normally can be easily identified by them having the the two vertical slits found on the threaded socket base. Note that it would also be possible to have an innard without the slits in an E.G.E. shell, but this would have been put together from older parts (right at the time frame of the merger) and really should be considered as Bergmann innards inside of an E.G.E. Shell

The General Electric Company took over in 1892. It is likely that G.E. sold out the remaining E.G.E. sockets and parts, however, so far there is no evidence that G.E. ever produced a moving tongue socket (or sold one with their name or the GECO trademark on it.

The oldest G.E. catalog that I have access to (so far) is 1894 and it does not contain moving tongue sockets.
We also have magazine and book ads from 1892 to 1894 with no evidence of the moving tongue ever being sold by G.E.
For these reasons, the moving tongue line up stops with EGE in 1892.

ABOUT INSULATED TIP MATERIALS
The tip used on the first turn key socket (Bergmann No. 1) was made of metal and the turn key itself was made of metal. There was an insulated piece made from hard rubber (vulcanite), which screwed into the turn key shaft and insulated the metal tip from the metal turn key. In the first socket there were two spring metal contact pieces that were slightly separated, in which connection was made when the turn key touched both pieces at the same time (thus the need to insulate the turn key from the tip.

The design of the turn key on the moving tongue socket is changed as seen in the patent. The tip is now made of an insulating material, which is designed to push the spring metal center contact (tongue) into the contact position. While the first Bergmann key used hard rubber for it's insulation, there is no evidence of the moving tongue socket ever using it. The patent for the moving tongue simply states "insulating-tip". My no. 1 moving tongue uses the red gelatinized fiber material for the tip. Many of my other early Bergmann's use gelatinized fiber as well, but at one point a different more durable green/brown colored clay based (likely Kaolin) and asbestos composition started being used. For more information about the identification of this clay based composition material, see my particle grain chart as well as the pictures below it which use this insulating-tip material as an example. For an example of the gelatinized fiber tip material see this link, where it is used in an example. (more on these materials soon).

DATING OF TIP MATERIALS
There is so much confusion in regards to the time frames of these insulating tip materials (from a dating standpoint).

I have no doubt that gelatinized fiber was used first, however I would expect to be able to state that it was used until a specific time and then this new material started being used. It is possible that both materials were used at the same time, or that one was used and then switched back, and then back and forth again.

There just seems to be no rhyme or reason of any kind, as for a time frame for the use of either material.

I have checked my sockets and have compared other collections, only to become more and more confused.

Possible causes of this material confusion could be that some turn keys may had been swapped out or changed on some sockets. It could also be that keys were mixed into a large bin at the factory, which always mixing could feasibly produce this constant mixture of materials through time. I really am not sure what the answer is, but I am sure of the fact that the material makes no difference as to any solid or useful dating criteria.

You can read more about vulcanized fiber here, gelatinized fiber here, or a note and detailed picture of the gelatinized fiber insulating-tip here,

MORE ABOUT INSULATED TIPS

For a quick inspection, you can simply shine a light down into the top of your moving tongue socket and inspect the tip. Note that some tips made of gelatinized fiber could be worn down, which in some cases can cause your socket not to work properly when turning it off and on. This can normally be adjusted by bending the spring metal just a tiny bit (rather then trying to repair the tip itself.
Sometimes you can come across a moving tongue that has a broken screw on the key shaft.	Picture showing a red gelatinized fiber tip	Picture showing a clay composition tip
In a case like this, a repair of some kind might be needed to produce a working socket. If the insulating-tip is broken or damaged, the best solution might be to replace the screw and file down the tip (from the back end) if needed. OR, if your piece is too small, pack the inside of the turn key shaft (just before the threaded screw hole, so that enough of the tip will stick out of the shaft to work the key when turned. The picture to the right shows a insulating-tip with a rusty broken screw piece stuck in the threaded hole. Other pictures show tips that became brittle over years and broke loose at the threads.

As shown described in the patent capture on your right (according to the patent), the first moving tongue socket used an insulating cement material to fill the screw holes. This cement can clearly be seen in the picture of the first moving tongue on your right, which was made of red vulcanized fiber.

This No. 1, is much different from all other moving tongue sockets. After this first socket, you will notice that all of the other moving tongues use a round sheet of mica as an insulator. From the picture above on the left, you can understand more of how the mica disk covered and insulated the screw holes, as shown in the picture of the disassembled no. 2 moving tongue sample. (also see the mica section for other Bergmann moving tongue sockets)

A better view of how the electrical cement (or fiber paste) worked, is more clearly seen in the picture of the broken vulcanized fiber plate shown below to your right in the next section called "Used Red Vulcanized Fiber".

This red colored (red lead pigment) electrical cement was invented, along with a series of experiments that resulted in several different cements and compositions. These were competed and documented between the dates of December 2 1882 and March of 1883. The cement experiments were documented in Menlo Park Notebook No. 143 which covered the period November 1882 to June of 1883. These notes document the chemical experiments made by George Gibbs and Thomas P. Conant on storage batteries, carbon filaments, cements for sockets, mica insulation for dynamo brushes and their experiments to produce marks on paper (probably for an electric meter). The last half of the book is by Conant alone and relates only to his electric meter experiments. Note worthy is that while this paste was used for as a composition material to construct fuses right away, it was also documented that lamp sockets were made (bulb bases). In fact it is documented that with each different mixture and test there was a socket made to see how it held up against different tests. (More about this topic here...) Even though this material was used on the vulcanized fiber socket about a year later (to fill screw holes), there is no documentation so far of any socket innards being made of these compositions, between the wooden Bergmann no 1 and this first moving tongue made of vulcanized fiber.

There is however evidence of plugs, fuse housing, switch bases and other electrical parts being constructed from these different materials during this time frame. While it is true that at later dates some of these materials where used as insulating blocks on moving tongues, it is important to know that it was not done during this time frame or before this vulcanized fiber version. We will get into which moving tongues used these materials as we progress through the moving tongue lineup.

During this time frame there were many complaints and problems being experienced with parts made of wood. Socket innards were swelling with moisture which caused expanding and breaking of the brass shells. There were also many shells that could not be taken apart because of the expansion; shade holders would not fit on to the shells any longer; switch bases made of wood were burning from arcing and high heat, etc.. For these reasons, great importance was being put on the testing of composition materials and the process of vulcanization. This includes materials that could be vulcanized such as rubbers, papers, fibers and the like.

In attempting to keep the costs down and because time was also an issue, many of these early products did not survive the test of time very well. This is seen in some of the early acorn sockets that more appear to be simply paper lightly glued together and now coming apart (as shown on your right).
A good vulcanized fiber product was several layers of paper, that was put through a chemical process. It was then compressed together and dried for a length of time. The drying and compressing process for a thickness of what is shown on your right would have been about a year and we know that this time was likely not taken on this sample or it lacked some other important step.

It is documented that Bergmann did test fiber product samples from different companies, but there is no way at this time to know which materials were manufactured by Edison companies; licensed to manufacture; or directly purchased from other companies. From reading through so much documentation including lab books, personal letters and notes, the first thought on Edison's mind when discovering a new chemical process or material, invention, etc., was "how" was it manufactured, and then off to the testing lab to try it out - thus making their own less expensive version.

When you read the moving tongue patent, you will notice that Bergmann clearly states that "I prefer to use a...material such as lava". While Bergmann did make this statement, it is also clear from the illustrations and text of the patent, that lava was an after thought. It was a statement that was most obviously added without updating illustrations or other text in the patent. It could be that Bergmann was already testing the new vulcanized fiber socket after the patent application was completed, but not yet mailed in. Likely he planned on using a new material, with what he called "lava" first on his mind.

This is proven by simple facts. First, the patent illustrations of the thickness of the insulated block being this fiber sample (shown right and below); the threaded Edison base shape also being made for this type sample; the cement paste was made to bind to this type of fiber material, not lava or asphalt (in this case

would had then been used for the paste); and finally the next socket (moving tongue no. 2) only months after the patent application was filed, is made of a black material that looks like lava. While it was not lava, this black composition was made from materials with volcanic properties. Also, notice the patent illustration shown on your right. Patent illustrations (as well as catalog illustrations) are most always drawn to scale, and will rarely look different from the current product (at the time the illustration is being drawn). There is no doubt when comparing the size of the insulated block in the patent illustration with the vulcanized fiber thickness, that this is what the artist was looking at.


So far, there is NO EVIDENCE of Bergmann ever using "lava", or "simulated lava" which was new at that time and growing in popularity. It is more likely that Bergmann simply changed his mind; or misidentified the material; or had a language gap; or misunderstanding of what sounded like lava to him. An example of this would be other products at the time that sounded "volcanic", or that were made from materials with volcanic properties. Examples of such names would be

Vulcanite, which can sound like something black and volcanic. However, I only used these names to point out their existence and how some names can sound. These examples (being vulcanized rubber) would not have melted during heat tests, as my Bergmann fragment sample did. After my testing and research, I know that the composition consists of the volcanic black pitch, asphaltum (mostly composed of bitumen). I trust that this is what Bergmann meant by the term "lava", since this was the next material to be used after the patent was filed. To make this case even stronger, I can document Edison using different asphaltum products such as Insulite. I also found a note from Edison in a technical notebook, written to Charles Batchelor to see Bergmann for a sample of a molded material. He gives the recipe of the composition which consisted of asphalt as the only binder.

The first moving tongue socket is not hard to identify seeing it is so different from all of the others that you will ever come across.

This was a really short time span (within only months) where rapid changes and improvements were being made. You will easily notice this fact from these first few sockets in this line up. This first vulcanized fiber moving tongue is not only the most rare of them all, but also likely to be one of the most fragile.

It was made from regular red vulcanized fiber, just like the acorn sockets were.
Unfortunately however this socket used more drilled holes and had moving parts, which applied stress to the insulating plate. Needless to say, these early innards were easily cracked and broken as shown in the picture to your right. If you find one of these (or other early 'lava' moving tongues) intact you should feel holy in some way. A word of caution, if you have one intact, treat it with kid gloves! - I have experienced intact sockets breaking into pieces, by simply turning the key. These first sockets however, because of the paper construction of the vulcanized fiber innards, do glue back together nicely. The black asphalt composition innards also are just as fragile. I have held many of these in my hand so far, with only two being found completely intact. These two also having cracks ready to crumble when you turn the key or tighten the socket collar. These can also be repaired and strengthened, but should never be thought to use as a working example on an actual lighting fixture. This is my personal opinion based from my first hand experience with them.

I would love to hear about or see any versions of these early Bergmann moving tongue sockets that differ from those that I show on this site.

From the original moving tongue patent illustration shown above, it is easy to see that the threaded base sleeve was much different from those found on the molded innards. Note worthy is the fact that molded innards started showing up only months after this patent was applied for in 1884.

Also notice that with the early vulcanized fiber innard, a much more crudely made sleeve was used. As shown on this sample (close up on your right), you will notice a sharp piece of brass sticking out from where it was cut and not filed down or trimmed later.

Also note worthy is the fact that while German silver was still used for the center contact of the No. 2 moving tongue, the example on this no. 1 moving tongue used a much thicker or wider version of it.

As seen above, this first moving tongue used a silver colored center contact (likely German silver) that is much wider then silver contact used on others that follow it.



As shown above, I can document the use of German silver on early Edison sockets. I also have come across purchases and continuous comments (Edison employee's) about German silver and Bergmann's special sources for purchasing the best quality of it. I can also document people at E.G.E. looking for those contacts after Bergmann was no longer with the company.

I can not however document its use on these early moving tongues, but because of the fact that these socket contacts are not plated they really can't be anything else. This is because nickel alone would be too hard and brittle and other silver colored metals at the time would have been too soft for this use. German silver was a well known metal of choice for electrical manufacturers for "spring metal" at this time in history.

WHAT IS GERMAN SILVER?

I know what you might be thinking, but I will stop you right here and now.

German "SILVER" is not the precious metal that you might be thinking of when comparing it to what you might already know about, such as Sterling Silver, Coin Silver, Italian Silver and many other more precious and well known terms.

German silver is an alloy that was made up from different proportions of nickel, copper and zinc.

Each manufacturer had his own recipe which may differ for their intended results. For example some would agree that the best quality (but also hard to work with) would be two parts nickel, four parts copper and two parts zinc.

However, if the items were to be stamped or maybe hammered, more copper would be added. If something was to be cast in a mold, some manufacturers state that two percent lead would also be added.

This German silver alloy is known to be harder and more durable then brass and can also produce a nice polished product.

Later, German silver was used for household items such as forks, spoons, teapots, etc., but plated with real silver over the alloy. This use however even though being German silver under the plate was no longer called or associated with it's name. These new products were called by names such as: navoline, argentoid, silveroid, nikeline (and some other names). Some of these can also contain small amounts of tin, cadmium or other white type metal.

German silver was only used on the first two moving tongue sockets (as well as all other Edison & Bergmann sockets made before 1884). After this point, brass and copper type metals are used.

The last patent date on the shell that these innards are found in is stamped MAY.13.1884. This was the patent for the Bergmann No. 1 socket with the wooden innards (assigned patent no. 298,658). The moving tongue (311,100) was patent applied for on April 10th 1884. So, we know that this socket material was being used sometime after May of 1884 because the date is stamped on the shell. We also know that the patent was approved on Jan 20 1885 at which time or shortly after the new patent date would had been added to the shell. I trust that we can safely date the innard materials (used on the sockets found in these shells) between these dates.

As far as the vulcanized fiber innards, it would also be safe to end their life several months before the patent approved date. This is evident from the fact that there are more socket innard changes coming up next in the lineup, which are also found in shells missing the Jan. 1885 patent date. We need to allow some time for these changes to take place in a manufacturing environment (even if it would be only a few months). From all of the patent evidence (and mention of lava), it is clear that there is no need to go out of our way and try to pin down exact dates for the vulcanized fiber innard, as this was an extremely short lived prototype.

As shown below, the first moving tongue used a bent wire screw terminal. Just as the shell and patent date example above, this bent terminal shows the short time frame between these socket materials. Innards 1 through 4 shown below are all found in these shells without quarter moon cut-outs on the caps and the the sockets own patent date, not yet found on the socket shells.

During this short 'patent applied for' time frame of about 8 months, we have a material change from vulcanized fiber to asphalt/lava, a center contact material change from German silver to brass and this terminal from bent to straight as well as a few other documented changes shown on this page.

You will notice that the older sockets (ones that are normally found without the quarter moon cut out on the socket cap), use these larger more primitive rectangle screws.

Notice three on the left side are shorter with less threads. These also have more perfectly shaped rectangles and clean and even slits for a screw driver.

The four on the right are fatter / thicker, longer and have different slits cut with no two being exactly the same.

These were made by hand and very crudely.

I first noticed (and thought) that the thread was different because it did not seem like these screws were fitting into newer Bergmann moving tongues. After a closer look it was evident that the new sockets were tapped / threaded, but not all the way through. Also because the smaller shorter screws are always used, they never need to be turned down into the hole that far where it would show.

However, because these older longer screws would require to be screwed into the brass further, it becomes tight where the female threads stop.

This is the reason that you will notice that the short screws work on the older sockets, but the older socket screws will not work on the newer sockets unless you tapped the holes further down.

Another thing noteworthy about these older screws is that they will not work on the older caps really well. With some of the screws, you might be able to fit them through the rectangle holes on the caps with much wiggling and fiddling, but most of them simply will not fit through the rectangle slots on the caps. A problem never heard of with the newer caps and screws. If you own one of these early Bergmann's just get use to completely removing the screw to remove the cap. Also for most of them you will need to use a very thin blade on your screw driver.

As shown and talked about already in this section briefly, the older moving tongue sockets (no. 1 through no. 5) do not have the quarter moon cut out. (Note that socket no.5 is not fully documented but based on some evidence)

It would probably be good to mention, that any Bergmann moving tongue without this cut-out is a really rare socket to come by. Jump for joy any time that you find one, but be sure that you take a closer look if you think that you spot one.

Always remember that the cap could be on backwards (you might not notice that the cut-out is on the opposite side, where it does not belong or show very well).

I will tell you that among my small group of collector friends, years had passed by before one of these had ever shown up.
In fact, it was only a good guess that one even existed for the longest time. We had deducted and reasoned that one had to exist, but had never seen one, or even a picture of one in a catalog. This is because Bergmann never updated his images of sockets in his catalogs once the first image was created. The only skinny Bergmann key socket ever shown in a Bergmann catalog was the no 1 Bergmann socket that had the wooden innards.

Another difference with these caps is that on the older one without the quarter moon, there is a bead / rib between the bottom of the cap ledge and the top ledge / border. This can easily be felt by running your finger up and down over the rib.

The newer caps with the cut-out do not have the rib. They only have a straight feel from the bottom and the top ledge.

The older socket without the cut-out has a bottom and top ledge as well as the RIB (or bump that sticks out).

It also has a third ledge or ring on the top, above the top ledge.

Note worthy is the fact that this older cap is of the same design as the Bergmann no.1 socket.
You might also want to view this section, where the inside of the cap is measured.

Starting with this no. 2 moving tongue, electrical cement is no longer used to insulate or cover the screw holes on moving tongue sockets. Starting with this socket, all other moving tongue sockets in this lineup will use mica as an insulator.

Noteworthy is the fact that the shape of the mica will change on the porcelain innards (lineup sockets 11 through 13) , to fit the new shape of the #3 Edison threaded sleeve.


Note that mica is also talked about in the first moving tongue section covering the topic of electrical cement in place of mica.

A BERGMANN RECIPE FOR A MOLDED ASPHALT COMPOSITION
Asphalt based compositions were not new to Edison or Bergmann, as their use of these materials predate his electrical inventions. In the early years Edison and Bergmann experimented and used hard rubber as well as different asphalt and rubber compositions for his other inventions, such as his phonograph in the late 1870's.

I can document several uses and testing of different asphalt binding compositions through the electrical years, but the best example is a laboratory notebook that I found belonging to Charles Batchelor (shown right).

The entire notebook contains his experiments and notes which were written in his own hand, with exception to the first page.

The first entry was by Edison in which he wrote some instruction about a molded composition.

Edison told Batchelor that he could get a sample of a good molded material from Bergmann (he gives his address).

Edison then describes the molded material as made from hard asphalt (Cuban or Syrian) mixed with a large percentage of kaolin (a natural clay material). It is then pressed in a hot polished brass mold from about 350 to 450° F.

There are also the 1882 (broken link) and 1883 (broken link) Edison defect books which also reflect an early use of tar and asphalt for insulation in wire tubes used for early underground wiring insulation.

As shown on the right, exposure to the sun on a hot day could cause the asphalt to soften and in some of the reports even run out of the tubes.

In another excerpt (shown right) 90 degrees for a softening (not melting) point is mentioned, which is close enough for refined Cuban asphalt which has one of the lowest melting points of 115-160 degrees depending on hardness. As a reminder, it was also the Cuban asphalt that was mentioned by Edison as being used by Bergmann in the Batchelor note book above.

You can read more about asphalt and bitumen based compositions using this link, or more about asphalt and its properties and history here.

THE REPAIR OF FRAGILE LAVA SOCKETS
Well, just to get down to the point of the material that was used on these sockets, it did not survive the test of time well.
So far all that I have seen have dried out, warped, cracked and become extremely brittle. I have handled several handfuls of these lava sockets to this date and only two were not broken in some way. One of these two broke into pieces when I turned the key on it.

Needless to say, I have had lots of experience in repairing these lava sockets.

I have discovered the best methods to not only repair these insulating disks, but strengthen and revive the material so that they are strong and ready for use once again. Most times when you see one of these in original condition, you will notice that it has become warped or bent out of shape. This change in the structure of the material has caused multiple cracks. This is because the parts were screwed tight and firm to the disk. The parts trying to hold the disk together actually caused cracking from the stress of the parts, which were forcing the disk to hold its shape.

Below are some close up pictures of a few repairs that I have done on lava sockets.

The first shown directly below, is of a Bergmann no. 4 lava moving tongue, which you can identify by noticing the straight wire screw terminal.

For anyone that is lucky enough to own one or more of these early moving tongue sockets covered so far, they can confirm the different cap issues that came along with these sockets.

For example the first sockets that used the fatter more crude screws, (in most cases) required the person taking the socket apart to remove the screws completely. This was because the screws were to fat or mis-shaped to fit through the rectangle holes. Later, when the screws were shaped more perfectly, you could turn the screw to line up with the rectangle hole and then simply separate the socket from the cap.

Another example would be that because of the shape and size of the brass skeleton, sometimes leverage was required to hold the cap in place while screwing on the collar. Rarely would the cap just fit into place and most times so much effort was required that sockets could be damaged simply by someone 'forcing' it to fit correctly in place.

This issue is/was caused by the skeleton not being bent to the correct or precise shape. Keeping in mind that this skeleton part when manufactured was one flat piece, it was then bent or folded over on the bottom and top which gave it the "L" shape. If it was bent just a bit too much (or not bent enough), the cap was hard to line up straight on the shell when screwing the socket tightly together.

The above could also play a part when lining up of the ground rounding into the top ledge of the cap. Since this piece was a thick flat (3mm) chunk of brass, when it was folded over, it was not completely round. To fix this issue and make the cap seat properly, the corners were ground off making the top of the skeleton perfectly round to fit into the top ledge of the cap.

All of the moving tongue sockets had the corners grounded until after 1890, when the skeleton design changed to perfect the porcelain version of the sockets. There were three different porcelain moving tongue sockets, which were moving tongue numbers 11, 12 and 13. Only sockets 12 and 13 did not need grinding and were manufactured close to or during the time period of 1891 / 1892.

Grinding corners through the years has always been really consistent.
This includes all eleven sockets that required grinding with exception to only this no. 5 socket.

To illustrate this statement, below I show the first five sockets and the grinding required to to fit the caps.
The measurement given is the size if it was not ground, illustrating how far off the cap would have been without grinding.
The cap would require the socket to be less than 31.31 mm for it to seat properly.


These measurements do not change because of any changes from socket to socket, but rather because they were all done by hand. The bending also would have caused small changes as well. Some were bent more or less then others causing the small differences. The grinding is what made the top of the skeleton round and to the correct size. You will find some sockets ground more or less then others, which sometimes because of incorrect bending would require more or less grinding.

The no. 5 socket is no different, it is the same 3mm thickness as the other sockets.
This tells me that Bergmann was on his way to fixing the cap design and possibly trying things differently.
Since this no. 5 socket is so different - new material, different size slot plate, and then this over grinding, it points to something much different. By the time the next moving tongue socket comes along, we have a new material change and a new style cap. This helps add to the evidence of this being more of a prototype moving tongue socket. Also about this time is found a new socket (rotary switch socket Bergmann No. 4) which uses the same soapstone material for it's insulated disk, and REQUIRES the cap change. It is evident that this moving tongue no. 5 socket required a cap without the quarter moon by the size and position of the new slot plate.

Only moving tongue sockets found inside of skinny Bergmann shells required the slot plate. In this lineup, this would be moving tongue's no. 1 - 7. Slot plates on all moving tongue sockets are 11.50mm high, with exception to this moving tongue no. 5 which is only 8.50mm. The positioning is also a bit different, but the main point is that it is evident that from it's size and position to require a cap without a cut-out. This socket innard was found in a box with a few caps without cut-outs, but no actual brass shell. It is possible that this was some kind of prototype socket, so if anyone else out there has anything like it, I would love to hear back about your socket similarities or possible differences.



Note that from the above it is evident that this No. 5 soapstone moving tongue sample used a cap without the cut-out.
However because this time period was close to when this change took place, we can not eliminate the possibility of a socket using this material being found using the new cap. OR, the next socket shown below No. 6 (made of gelatinized fiber) being found in a shell without a cut-out on the cap.

Note that the socket before this one (the moving tongue No. 5 soapstone socket) used a cap without the cut-out on it.

Since this time period was close to when the change took place, we can not eliminate the possibility of either a No. 5 socket with a cut-out, OR this No. 6 socket (made of gelatinized fiber) existing in a shell without the cut-out on the cap.

I talked about gelatinized fiber a bit in the introduction part of this page in the section called Insulated Tip Materials.
I also made a small table with links called "insulating material known to be used on moving tongue sockets".
The topic of gelatinized fiber along with a good background history is covered here and some pictured examples of different types of fiber are linked here. I touched on the differences between the EGE and Bergmann moving tongue sockets here in this section, which also comments on and talks about the gelatinized fiber versions.

As you can tell from these links, I have already gone into lots of detail on gelatinized fiber.
I am still looking for some quotes that I dug up a while ago, which were a few different telegrams going back and forth between Edison and some others, about Bergmann meeting with someone to try out the new fiber. When I find them again, I will link it here as it will help with dating.

While all of the sockets in this list (including this shell) are extremely rare to come by, it is this material (gelatinized fiber) that will seem most common to you in your search for Bergmann moving tongue sockets. Most of the ones that you will come across will be the fat Bergmann shell designs, some fiber and some porcelain (porcelain being EGE not really Bergmann) but don't worry - you will come across one of these gelatinized fiber skinny's from time to time.

Gelatinized fiber was the insulating material of choice for Bergmann when it comes to moving tongue sockets.
It was used on this no. 6 as well as no. 7, 8 & 10. No. 9 was a new composition being tested, and 11, 12 & 13 were EGE sockets made with porcelain innards.

Gelatinized fiber was, is and always will be the material loved by those that used these sockets back in the early days, and those that collect them today.

As shown in the picture on your right, the first shell is the no. 6. The shell next to it is standard long skinny Bergmann shell design, which is pictured so that you can compare the difference.

It is unknown as to why this shell is shorter then all other long skinny moving tongue sockets. It is obvious that the space under the ornate rib is shorter, but there are some different thoughts as to why.

Some think that the collars (flanged rings) at the time were much thicker or higher.

These thicker collars would have covered most of the exposed threads (though the electrical codes at the time did not require this).

It is also true that there was a migration of different types and materials for these collars; The first Bergmann turn key socket used wood and then was later documented as being upgraded to hard rubber. The patent for the moving tongue documents that collar as "a flanged ring, K, of hard rubber or other suitable insulating material, is screwed between sleeve B and shell I". I should also mention that I own a thicker collar (obtained from one of my short moving tongue sockets) that is made of a wood and fiber based composition. This proves to me that there was experimenting in progress to some degree, because of it's existence. However, this is not proof as to a reason for the existence of the short shell. As shown in the pictures below, the thicker collar would have covered the threads completely, if a standard Edison shade holder was placed between the collar and the socket shell tube.


Others feel that the short socket tube had to do with shade holders. There is a Bergmann shade holder that was applied for patent on Oct 9, 1882 along with the first acorn socket (patent no. 293,552). While in 1882 this holder was similar to the standard Edison holder, some time after it's patent approved date of Feb 12 1884 (because the date is on it and not marked patent applied for - so, possibly before), a built in hard rubber collar was added to it. It is however documented as existing with the collar Sept. 26, 1885 (see below).

This shade holder would hide the extra threads under it. However, it could also have been used with a standard hard rubber collar which would then allow the shade holder and shade to be used under the first collar by screwing it tightly on to the exposed threads. So, it is also possible that the short shell design, was to accommodate this type shade holder. There is a patent (no. 361782 some illustrations shown below) that illustrates this shade holder with two collars, but with the second collar screwed on to the exposed threads. This patent also helps date the collar being added to the holder having a patent applied date of Sept. 26, 1885, which means that at least we know the collar was added to the holder by that date.



It is also noteworthy that without the two collars, If the shade holder was removed while the socket was on a fixture, it would have fallen apart. So, by using two collars, the first one would hold the socket together while you were still able to remove the shade or holder that was screwed on to the exposed threads under the first collar.

So, maybe you can think of other reasons or 'special purposes' for this short shell. Let me know and I will post them up here for others to read. I guess both of these could be correct too, if taken in the light of this socket being used with this shade holder and the thicker composition collar used if the holder was no longer needed.

Another mystery about this socket.

THERE ARE NO PATENT DATES ON THIS SHELL
If you follow these types of sockets, you will know that Bergmann turn key sockets always have dates on them, unless they were rubbed off during an aggressive cleaning. HOWEVER- in these cases, you will always find at least a few numbers or letters showing through somewhere on the shell (even if only lightly).

METHODS OF DETECTING PATENT MARKS
There are also other ways to tell if a shell has ever been stamped. Here are some quick guide lines for your use. First, you will most always notice at least some of the dates or letters stamped through to the inside. The early sockets guessing 1884 through 1886 appear to have been stamped by hand, not always being even or at the same place on the shell. If you are holding the shell with the key hole facing towards you, these stampings will mostly be positioned at twelve o'clock, but some will be at either one o'clock or eleven o'clock (just a bit off).

Another method that you can use is a measurement of the shell thickness. If you measure the shell by the stamping area (using a digital caliper), you will notice small (but very noticeable) variations in thickness where the metal was hit.

Also, if you examine the inside of the shell from the eleven o'clock to the one o'clock positions, you will notice where the finish/lacquer has been scraped away or at least a noticeable rectangle shadow where it was stamped. I have become really good at noticing this by taking the blind test with about 20 or so shells in front of me. Not looking where the dates were stamped (covering the outer shell with my hand), looking into the shell while turning it and finding the exact place where the shell was stamped every time. (if you ever try this, always be sure to not mix up your innards or caps as it is important to keep your sockets all original).

I am guessing from my samples (based on those missing the 1885 date), that somewhere close to 1886 a new method was used to stamp the shells. This new method caused only light dates (hard to see) to appear on the outside, no metal stretching (so no thickness changes) and only the shadows on the inside of the shell (without the dates bleeding through). Later (about 1888) with the thicker fat Bergmann shells, something changes again as almost ALL of the dates can be seen coming through to the inside of the shell (not just a few letters and numbers as in the later thin long skinny shells).

See below where I show some shadows found on some of my long skinny shells.



Here are some full size images in a PDF (broken link) so that you can zoom into the edges and have a closer look if you care to.

Now that we have covered the fact that we can tell if a shell has ever been stamped, I should bring up the point that these short sockets show no dates or individual letters or numbers ANYWHERE inside or out. I will also mention the fact that I took hours with a high powered microscope on all four of my sockets. They also have no stamping shadows on the inside of the shell and the thickness does not change around the diameter of the shell.

I have no real good answer as to why these shells do not have patent dates on them, since the shells before them and right after them did. Off the wall guesses would be that possibly the stamping method used, required the longer shell to fit some kind of die to be stamped. Another thought would be that since stamping methods did change about this time, maybe they were in wait for the new machine or what ever was needed or required to complete the task.

I should also mention that there is nothing to document that this no. 6 and the upcoming no. 7, fall into these numbered positions. The only difference between these two sockets is the shell size and the patent dates (back on the shell). The innards are the same. In fact, since the number 8 moving tongue is a fat Bergmann shell, maybe it would make more sense to say that the method for the stamping of the shells did need to change and this was in progress at the time. Well, we really do not know - I just present these thoughts to make you aware of the different possibilities, in hope that something will make sense for now, until (hopefully) at some future time we learn more.

For my test bed (of short long skinny's), three have been obtained from one source and another from a completely different source - all four matching in size and missing patent dates. It is evident that these sockets were not just a fluke or modified by someone for some special use and so become part of this socket lineup.

Just as all other moving tongue sockets, this shell is of the normal size for long skinny's.
As shown above in the socket no. 6 section, that gelatinized fiber socket used a shorter skinny shell.

Also, this no. 7 moving tongue socket, shows the patent dates, which also now includes the Jan 20 1885 patent date (no. 311,100) which was for the moving tongue itself.

Keeping in mind that moving tongue no. 4 (and those before it), did not yet have the date on them. You will also remember that no. 5 was found in a box without a shell (but proven to still use a cap without a cut-out), we still do not know if it would have used a shell with or without the 1885 patent date on it. NEXT, we have moving tongue no. 6, which did not have patent dates - SO, in this lineup, this moving tongue no. 7, is the first documented socket to have the 1885 patent date on it.

If you have a no. 5 or no. 6 socket with patent dates found on the shell, I would sure like to hear about it - please do contact me at my email

Up until this time in history, Bergmann had been manufacturing the 'long skinny' sockets and shells.
It is not documented exactly when this change took place, but we can document for sure the date of the second Bergmann rotary switch socket which was illustrated it in a FAT shell. Since this socket's patent was applied for on June 2 1888, we know that these shells existed at this time in history.

DATING USING CATALOGS
One draw back with finding an earlier date that I have talked about before, is the fact that Bergmann did not update their catalog illustrations. Once an item was illustrated (a picture drawn for that item), that item will always look the same in future catalogs, even though the item might go through several different upgrades or changes. An example of this (there are so many) would be a catalog in 1889 (Bergmann's last catalog) that still shows the no. 1 key socket (1882 socket) even though it went through many different changes (example this FAT shell). Acorn sockets also still show the no. 1 ribless acorn which is also already nonexistent for so many years (see ribless acorn dating dilemma for more info). Also, another problem existed when resellers in wholesale electric catalogs, used those same out dated images for their new catalogs.

DATING USING OLD ILLUSTRATIONS AND HISTORY
Concerning Bergmann items, a life saver for researchers is when an inventor uses a Bergmann socket to illustrate his invention (maybe a lamp shade) and has an illustration made (which will now document the socket's existence at the time and date the illustration was published). So, since Bergmann catalogs did not change their catalog illustrations, most times we need to document Bergmann socket changes by locating the first appearance of different shells in the history of patent illustrations, ads or catalog images of other inventions. However, at this time we have not found any that pre date the rotary socket patent.

DATING USING PATENTS
The first actual Bergmann documentation for this FAT shell the patent for the rotary switch socket (patent 389,280) which was applied for on June 2 1888. Since this is a FAT shell socket, we know that FAT shells existed when this patent was applied for. So, to get even closer, we would need to find documentation that shows an illustration of a FAT shell before June 2nd 1888. Unfortunately, at this time we have not found anything to document this. If you come across anything, please do share (so that the information can be made public.

DATES ON SOCKET SHELLS
Another method for dating would be a fat shell that contains (or is missing) a patent date, but not yet another. For example, if we had two (or more) sockets that we could trust (meaning from two or more entirely different sources) we could date changes about socket innards, caps and outer shells. Hypothetically: Lets say we have moving tongue sockets -without- the 1885 patent date; and caps -with- the quarter moon cutout. This would tell us not only that the cut-out was used before 1885, but that the skinny rotary socket did as well (since the quarter moon style cap was originally made for that socket). To use this type of dating method in this case, we would need a FAT shell with a patent missing that was before it's patent date of September 11, 1888. This would tell us that the FAT shell most likely existed during that time since the date was missing. Unfortunately, the closest patent date possible going backwards would be the moving tongue patent Jan 20 1885. So going backwards if these FAT shells existed during this time, we could hope to find one missing this date which is likely not possible since we have skinny shells with the 1885 patent date. The closest date moving upwards, is the rotary switch patent which was applied for on June 2, 1888 and approved on September 11, 1888. So, the only thing that a patent date could do for us here in this case, would be if we had a rotary switch in a FAT shell that was missing it's own patent date (which we do), but unfortunately this only tells us that the FAT shell existed before the patent approved date of the rotary switch (September 11, 1888) and we already know this because the FAT shell is illustrated in the patent itself. So, using this method did not produce anything that we would hope for. However, later we will find some use for this method when dating E.G.E moving tongue (and other) sockets using the 1890 patent dates.

So, basically this is the long way around showing you -why- we can only document these socket shells to 1888 so far.
If you can share any information to document these FAT shells any sooner, your information would be more then welcome.
Please mail to

As shown below, the new FAT shell has a new and different shell cap design.
The cap no longer uses rectangle screws, so it no longer has rectangle screw holes. It now has the round screw hole along with the turning slot as shown below in the cap picture on your right.

The first cap was used on the first Bergmann turn key socket (patent no. 298,658) applied for patent on October 9th 1882 and then used on moving tongue sockets 1-5. The second cap was used on the first long skinny rotary socket that will be covered in the upcoming Bergmann Socket No. 4 line up section. It is sometimes called the "Mystery Socket" because it has unknown patent information, but is seen in three patent illustrations for a Bergmann glass shade with screw threads and/or shade holding system using a hard rubber collar. This patent was applied for on October 16th 1885 and was assigned patent no. 337336. This patent is (so far) the earliest known date for this socket and cap. The third cap was used on the last Bergmann FAT socket shells. It was then used on E.G.E shells when Bergmann & Co. merged into the Edison General Electric Company (1889), until "General Electric" (Thomson/Houston) took it away from Edison in 1892.



You can also see the section above for the first moving tongue socket, where I talk about and compare the first and second caps to each other. I also talk about and measure the inner diameter of the cap for moving tongue number five here.

As shown in the images below, the new FAT shell design also took on a fat plain rib.
Noteworthy is the fact that about the same time that this took place, the standard keyless socket at the time (the acorn socket) also took on a fat plain rib (see here for more info).



The plain rib lived on through all of the rest of the moving tongue sockets.

The long skinny socket shells that we have covered up to this point, were all marked with a series of different patent dates with the word "PATENTED" stamped directly above the dates. Up until now there have been no company names marked on these shells. However, starting with this socket moving tongue shells are now marked with the company name.

Below is a table that covers all of the markings on the moving tongue shells.

For links to moving tongue patents and additional info, see my Bergmann patent info chart.

Note that I have changed the color of dates to pay special attention to, in hopes to make it an easier process to compare your socket shell dates.

LONG SKINNY SHELL DESIGN
Moving Tongue No. 1 Moving Tongue No. 2 Moving Tongue No. 3 Moving Tongue No. 4	PATENTED Dec 27 1881 May 2 1882 Jan 10 1883 Feb 12 1884 May 13 1884	5 Patent Dates BERGMANN SOCKET No Jan 20 1885 Date
Moving Tongue No. 5 Moving Tongue No. 7	PATENTED Dec 27 1881 May 2 1882 Jan 10 1883 Feb 12 1884 May 13 1884 Jan 20 1885	6 Patent Dates BERGMANN SOCKET
Moving Tongue No. 6	No Patent Dates	No Patent Dates BERGMANN SOCKET
FAT SHELL DESIGN
Moving Tongue No. 8A	PATENTED Dec 27 1881 May 2 1882 Jan 10 1883 Feb 12 1884 May 13 1884 Jan 20 1885	6 Patent Dates MANUFACTURED BY BERGMANN & Co. N.Y. (horizontally) Patent Dates (vertically) Note that this shell still has the Jan 10 1883 date
Moving Tongue No. 8B	PATENTED Dec 27 1881 May 2 1882 Jan 10 1883 Feb 12 1884 May 13 1884 Jan 20 1885 Sept 11 1888	7 Patent Dates MANUFACTURED BY BERGMANN & Co. NY (horizontally) Patent Dates (vertically) Has the 1888 patent date and is the last "Bergmann" moving tongue shell. Note that this shell still has the Jan 10 1883 date Thanks goes to David Christian from our forums who provided this image.
Moving Tongue No. 9A Moving Tongue No. 9B Moving Tongue No. 10	EDISON GENERAL ELECTRIC CO. NEW YORK U.S.A. PATENTED Dec 27 1881 May 2 1882 Jan 10 1883 Feb 12 1884 May 18 1884 Jan 20 1885 Sept 11 1888	7 Patent Dates EDISON GENERAL ELECTRIC CO. NEW YORK USA PATENTED (everything horizontal) May 18 1884 was mis printed on this shell. It should have been marked May 13 1884 Note that this shell still has the Jan 10 1883 date
Moving Tongue No. 11	EDISON GENERAL ELECTRIC CO. NEW YORK USA PATENTED Dec 27 1881 May 2 1882 Oct 3 1882 Feb 12 1884 May 13 1884 Jan 20 1885 Apr 15 1890	7 Patent Dates EDISON GENERAL ELECTRIC CO. NEW YORK USA PATENTED (everything horizontal) Jan 10 1883 was removed and replaced with the Oct 3 1882 patent date (also on future shells) Sept 11 1888 removed from this and future shells Apr 15 1890 was added
Moving Tongue No. 12 Moving Tongue No. 13	EDISON GENERAL ELECTRIC CO. NEW YORK USA PATENTED Dec 27 1881 May 2 1882 Oct 3 1882 Feb 12 1884 May 13 1884 Jan 20 1885 Apr 15 1890	7 Patent Dates EDISON GENERAL ELECTRIC CO. NEW YORK USA PATENTED (everything horizontal) ALL N's on this and future moving tongue sockets are stamped backwards

NAME CHANGE FROM "BERGMANN & CO." TO THE "EDISON GENERAL ELECTRIC CO."
Important here at this point in socket history, is to have a clear understanding of who Bergmann & Co., Edison General Electric Co. and the General Electric Co. where I talk in a bit more detail about the company history in the GECO area here, and the lighting time table here. In a nutshell though, Bergmann & Co. was basically Edison & Bergmann. In 1889 Edison had a disagreement with Bergmann and bought him out. Bergmann & Co. Was consolidated into a new company which was named "Edison General Electric" (E.G.E.). The older Bergmann & Co. Was a partnership between Bergmann & Edison which was dissolved when E.G.E. (Edison's new company) was created. In 1892 Edison lost controlling interest in his electric companies and was bought out by Thomson-Houston. At this time E.G.E. And other Edison electric companies were consolidated into a new company called "General Electric" (G.E.) which was basically the Thomson Houston Electric Company (which now owned rights to the "Edison" name as well as (electrical) Edison trademarks). When Edison's consolidation took place, the FAT Bergmann socket shells started being marked with the new "Edison General Electric" Company name.

SOCKET STAMPING CHANGED TO HORIZONTAL POSITION & MIS PRINTED PATENT DATES
At the time of Edison's Bergmann & Co. take over in 1889, there must had been some major confusion taking place. I have read excerpts where those now in charge, were asking around and confused about where Bergmann was purchasing different items from, as he did not keep very good records. It was also a time in history when changes were being made which could have also added to some existing confusion. An example of one of these changes would be a major material change in socket innards form fiber to porcelain. Along with the company name change, came a necessary change to the stamping of patent dates on the socket shell. In order to fit the new name comfortably on the shell, a change in design was made which was to now print the patent dates and company name in the horizontal position. It was probably during the first run of this new design that the May 13 1884 patent date was mis printed as May 18 1884 (shown below). Later (after fixing the patent date) another type setting change was required, at which time all of the letter N's were printed backwards (which I believe to be an indication of a continued confusing environment). For more about dates on shells see the date chart

MOVING TONGUE NO 9-A USED GELATINIZED FIBER FOR THE INSULATED DISK
The key to placing these two socket innards in date order, is the fact that gelatinized fiber EGE socket innards with slits in the threads existed (no 10). The patent for the slits was applied for on October 18th, 1889 by the Edison Lamp Company. The patent was approved on April 15th, 1890 and assigned patent no. 425741. The fact is that if you have a FAT shell marked Bergmann & Co. And it uses innards that have these slits, those innards were from the time of E.G.E. And not Bergmann as evident from the slit patent dates. These case scenarios could have resulted from E.G.E. using up older parts and inventory, or from supply houses or jobbers doing the same.

MOVING TONGUE NO 9-B USED AN UNKNOWN COMPOSITION FOR THE INSULATED DISK
Taking into account (shown above) that there were fiber examples of EGE socket innards using slits, we must date this socket before or right at the same time as those since these innards do not use them. In fact, this could also be a Bergmann invention housed in an EGE shell, which is more likely. From examining the condition of the sample, it was obviously a failure as a material to replace gelatinized fiber. During this time frame and the change to an insulated disk made from porcelain, E.G.E. could have been using up all of the older inventory including old failed prototypes.

UPDATE & AFTER THOUGHTS
While getting ready for the next section (the Bergmann no.4 rotary switch socket) I remembered that the FAT version was popular for using an after market turn key (likely Mitchell Vance), that also used an unknown composition for the innards. I bring this up, because these innards are pictured in a Bergmann shell. When examining my photos, I believe that the composition might be the same as pictured here, only in better condition. I also now came across pictures looking through our forums (linked here) of what looks to be the same composition, that is also in a Bergmann shell.

Take note now that both examples are pictured in shells without the 1888 patent date. Also that we commonly come across Bergmann and E.G.E. Sockets that use gelatinized fiber that have the 1888 patent date.
This only leaves three seemingly logical conclusions to arrive at:

1. Bergmann started using gelatinized fiber and switched to the unknown composition and then back again, and then later E.G.E. decided to try it again and switched back as well.

2. Bergmann used both side by side right through the time of E.G.E.

3. E.G.E. Or possibly even G.E. in 1892 (but less likely), was simply using up all of the old socket parts.

I will be spending more time testing this composition (as well as comparing the rotary composition), after I complete these Bergmann sections. For now (just taking a quick close up look), this unknown composition might be a mica based composition. This thought comes from my example definitely having lots of shinny flakes of mica in the cracks and comparing the look to other mica based composition inventions that I have put on the side for research time.

THIS SOCKET MARKS THE START OF USING SLITS CUT INTO THE THREADED BASE

The slits are a great dating tool for early sockets and sometimes help make a positive identification between Bergmann and E.G.E. socket innards. The original purpose of these slits, was to help hold the bulb in place so that it could not vibrate loose.

While it may have been good for bulbs, it clearly was not a good idea for the sockets. These slits caused damage to socket threads by creating a weakness in the metal. When the socket collar was stuck or tight, the threads cracked and broke easily.
Once cracked, the problem even became worse as the hard rubber collar got stuck on the cracks when turning it. This caused the threads to break apart or crack even more.
The original patent for these slits was applied for on October 18th, 1889 by the Edison Lamp Company. The patent was approved on April 15th, 1890 and assigned patent no. 425741.

If you have an E.G.E. Socket shell without the April 15 1890 patent date, but the innards have the slits, it is a good chance that the socket falls between the patent applied for time and the patent approved date.

Since there are no other changes documented on innards from the time of Bergmann gelatinized fiber until these slits, it is a common concept that gelatinized fiber innards without slits are Bergmann innards and those with slits are E.G.E. innards.

THE FIRST PORCELAIN INNARDS
This is the first socket that uses porcelain as an insulator for the insulated disk.
This socket also ushers in a few other basic changes, while the next two moving tongue sockets bring us to only a couple more minor changes and the end of this unique and historical socket

THREADED PORCELAIN INSULATED DISK
The first minor difference that will help you to identify this unique 'first porcelain innard', is the fact that (just as all of the others before this socket) one of the sleeve screw holes in the insulated disk is threaded. In the next porcelain version of the moving tongue a smooth hole of a larger diameter is used, with a nut that holds it on the other side.

You might had noticed that in the pictures of moving tongue no. 9-B (the unknown composition socket), that it was also shown using a nut. However, the hole on moving tongue no. 9-B was also threaded. It only uses the nut out of necessity now, because of the deteriorating condition of the composition material that was used for insulated disk. This first porcelain socket uses the threaded hole, which seemed to work well from the examples that I have of it. Others may not had been as lucky as me though, since it was soon changed.

One fact with porcelain, was the shrinkage during firing. It could had been that it was simply not as accurate at the time, or to mold the hole was just harder to do.

A screw and nut likely seemed like a quick and easy solution to what ever issues that they came up against.

As shown in the clip from a 1905 Marshall Electric Manufacturing Company catalog below, it is stated that about twenty years ago it was "impossible" to get to any degree of accuracy.

It also states that porcelain pieces shrink about 1/7 of the diameter of it's original un fired size.


STARTING WITH MOVING TONGUE NO. 11 THE SKELETON KEY HOLE USES A BUSHING

You will remember that the long skinny Bergmann sockets (which were before the first FAT Bergmann moving tongue no. 8) used a regular hole, but with a slot plate to cover the key hole cut into in the skinny shell. Up until now, all FAT shells simply had a hole drilled through the skeleton (as shown on your right). On the other side, the key slides into a bushing that is soldered to the skeleton as shown in the picture below.

Starting with this socket the key bushing is no longer held in place by solder, but as shown above on your right and the picture below a new crimped bushing is used.




STARTING WITH NO. 11, A CHANGE TO THE POSITION OF SHELL WORDING TAKES PLACE

As you will notice on the other E.G.E. moving tongue sockets that we have covered so far, the word "EDISON" has been alone on it's own line and the words "GENERAL ELECTRIC" on the next line.

Starting with this shell, the font lettering grows larger and the words needs to crunch together more to fit properly. Now, the first line has "EDISON GENERAL" and the second line continues the rest of the company name.

MORE ABOUT THE MOVING TONGUE NO. 11
This is the first socket to use shape design no. 3 of the Edison Sleeve which you can read more about by clicking here
This is the first socket to use the second shape of mica as an insulator, which you can read more about by clicking here
Starting with this shell the patent dates Jan.10.1883 and Sept.11.1888 are removed, and the patent dates Oct.3.1882 and
Apr.15.1890 have been added. For more information about this change you can see the patent date chart for moving tongue no. 11 by clicking here

For other general information about this socket see it's introduction page by clicking here

A NUT IS NOW REQUIRED TO HOLD THE SLEEVE SCREW

The no. 11 moving tongue had a threaded hole through the porcelain, which did not require a nut to be used to hold the sleeve on one side. Starting with this socket, a molded square hole is provided to house the square nut. There is more information about the threaded hole and porcelain molding in general in the moving tongue no. 11 section. Click here to view the area if you have not yet read it.

A NEW SKELETON SHAPE

Starting with the no. 12 moving tongue, a new method of manufacturing the skeleton takes place. With the new method, the skeleton no longer requires grinding at the corners to fit the cap.


A TYPE SETTING ERROR ON THE SHELL TAKES PLACE


For some reason undocumented at this time, the Edison General Electric company decided to change the typesetting on their shell once again.

There were not any patent date changes that were needed, but the font type and size does change. This could suggest that this initial change was being made to solve a problem that a smaller foot print would solve. One such flaw that would have been repaired would be the L in the word "GENERAL" which on many shells would be partially hidden under the cap rim. Another solved issue would have been where either the first line or in some cases the last line would be stamped lightly (in some cases to shallow to read clearly). This would have been caused by trying to flat stamp the shell into it's curve or bend. The first and or last lines would not be as deep. By making the type smaller, the stamping would not stretch as much to the curve on the shell and would have fixed this issue.

This moving tongue and the one below which is basically the same only with a hard rubber key, are the last documented moving tongue sockets (both of which had the backwards N's).

THE HARD RUBBER KEY
This moving tongue is virtually the same as no. 11, only with the black hard rubber key in place of the old Bergmann style brass turn key.

There is not much documentation on the hard rubber key, it is possible that it was sold at the same time as the cast brass key at one time. It is also possible that the cast brass key was discontinued at one point and only this hard rubber key was offered. The only documentation so far is the fact that it was not offered as an option in the Edison General Electric catalog and price list dated November 1st 1890. It was also not offered in the September 1st 1891 catalog. General Electric took over Edison General Electric in mid 1892. In December of 1892 (as shown below) General Electric pictured the socket in an ad in the December 31st Electrical World magazine, which still used a brass key in the illustration. A brass key is also shown in electrical catalogs, without a mention; order number; part number; telegraph code or price for a hard rubber key version. The current catalog availability and those checked so far are: 1891 Gate City Electric, 1892 Electrical Supply Co., 1893 Pettingell Andrews Co., 1893 Taylor Goodhue & Ames, 1893 Central Electric Co., And 1895 E.P. Gleason.

Even though it is included as late as 1895 in the E.P. Gleason catalog, I should mention that G.E. did not sell this socket by the time of their 1894 catalog. You will also find this socket with the cast brass key in other catalogs even later in date, but these occurrences can only be electrical supply dealers having such a large quantity that they lasted a while. In fact, even though it is shown in the December 1892 Electrical World magazine, it is also not proven that G.E. Ever sold or offered the socket, other then simply selling out the old stock. All of the hard rubber keys are marked E.G.E Co. And no moving tongue sockets with keys marked G.E. Co. have turned up to this date.

The 1894 General Electric catalog shows G.E selling their new key and keyless sockets, but no moving tongue FOR SALE (.)

There is however in the 1894 General Electric catalog an image that was most likely taken directly out of an older EGE catalog, which shows the socket in use while selling rosettes.

The illustration shown above was only used to sell the ceiling rosette, the socket shown in the illustration was only to show how the part worked and was not for sale. Having the socket updated in this illustration, also helps to add proof that possibly at one time the cast brass keys stopped being offered. The argument being that there would have been no other reason to change the illustration.

THIS BERGMANN SECTION IS STILL BEING WORKED ON - PLEASE CHECK BACK SOON...

Where to go from here?

THE BEGINNING HERE
http://www.antiquesockets.com/bergmann1.html

Or see the new materials section still under construction...