This first insulator constructed to hold the wire by suspension on American lines appears to have been used in 1849. Credit for this mode of insulation has been attributed to two different people. One source states it was devised by John J. Speed, Jr. and used on a line between Detroit and Dearborn, Michigan, in that year. It was made of a cast iron casing with two glass interior parts which held the iron hook in place.
Amos Kendall (The Telegraph in America, p. 113)
Another source gives credit to Amos Kendall as the inventor of the suspended hook. Regardless of who was the first to design the method, this type of insulator saw widespread use by a number of different telegraph companies. Dozens of varieties were manufactured over the next twenty years. Some were very simple and made use of only an iron hook embedded in rubber or vulcanite. Others were composed of various parts consisting of glass and paraffin with iron covers. Two of the more widely used patterns included the Lefferts type and the Brooks paraffin insulator.
Marshall Lefferts (The Telegraph in America, p. 113)
The Lefferts hook is named after Marshall Lefferts who had a large business in New York City which supplied telegraph wire. It consisted of a glass cylinder into which an iron hook was embedded. A small groove or notch was molded into one side of the glass. The insulator could be inserted into a hole drilled in the underside of the crossarm or in a block of wood. It was held in place by a wooden dowel or pin, driven through the arm or block, and received by the notch molded in the side of the glass.
Lefferts suspended hook insulator showing horizontal groove which would
accept a pin to hold the insulator in the block of wood. The base of the
glass has four triangular impressions, one in each quadrant of the base.
An actual split crossarm showing the installed Lefferts hook with
the wooden peg used to lock the insulator into position. (Smithsonian
Institution)
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Unless otherwise noted, photos by John and Carol McDougald
The Lefferts hooks were largely employed on a line between Boston and New York City by the New York and New England Union Telegraph Company which was organized in 1849. They were also used by the Atlantic & Ohio Telegraph Company and in later years by the American Telegraph Company. It is likely several lines made use of them in the East. Lefferts became involved with various companies as an officer and could easily have used his influence in supplying wire, insulators, and perhaps other telegraph supplies.
As was mentioned previously, the Brooks paraffin insulator was another suspension type which was produced in large numbers. David Brooks had patented this insulator on August 6, 1867, and during the late 1860's produced vast numbers of them. It was reported that during peak production as many as 15,000 were manufactured in the span of one week. They consisted of an iron shell into which was cemented a glass cylinder, similar in shape to a bottle. An iron hook was mounted into the glass cylinder for receiving the wire. The interior surface was coated with paraffin which at the time was highly regarded for its insulating properties.
An advertisement for the Brooks paraffin insulator which appeared in a catalog of the L.G. Tillotson & Co. Note the unit price for each application.
Brooks Paraffin Insulators (Smithsonian Institution)
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Unless otherwise noted, photos by John and Carol McDougald
In David Delling's Before Threads, there were nine marking variations for the Brooks 1867 paraffin insulators. Only six variations have been located that match Delling's references. The markings are on the flat heal of the iron cylindar.
Brooks Side Screw Paraffin Insulator (Smithsonian Institution)
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Unless otherwise noted, photos by John and Carol McDougald
The side screw Brooks insulator is extremely rare. To date, there are only has three known specimens, one of which the author photographed at the Smithsonian Institution. The piece is embossed on the heal with three patent dates -- Nov 29 64, Aug 6 67, July 26 70. Filed by William H. Dechant, assignor David Brooks, the 1870 patent covered an improved cramp-hook which was designed to prevent the wire from being dragged off the supporting-hook by upward strains. Earlier Brooks insulators were constructed so as to prevent the wire from falling, but not so as to prevent it from being lifted off them.
Although Samuel Morse had patented his method of telegraph, there was nothing to stop another inventor from devising a system different enough from that of Morse to allow its use without patent infringement. One such man was a Vermonter by the name of Royal House. In the early part of 1846 he applied for a patent for a telegraph printing instrument. This instrument, rather than indicating a message of dots and dashes, printed the message upon a paper tape in Roman numerals. Lines using the House machines were built to create direct competition with those using the Morse system.
An insulator used on the House lines consisted of a coarse glass screw-like surface formed inside and out, as shown by the darkened area in the drawing. It was cemented into a bell-shaped iron cap as shown.
Pole top installation and cut-away drawing of the House insulator.
This large insulator, weighing from three to four pounds, was then fitted on the top of a pole which had been prepared to accept the arrangement. The line wire was held in place by the projecting points on the top of the iron cap. Although the House insulator saw extensive use on the lines using his system, only one surviving example is reported and resides in the Smithsonian Institution. No complete units have been reported by collectors, although fragments of both the iron shell and various colors of the glass cap have been found on the route of an early line constructed in Ohio.
House's Printing Telegraph envelope dated 1850. Advertisement reads: "Only Direct and Reliable line to New York, connecting with Boston, Buffalo, and intermediate stations." (Licari collection)
Only known complete House insulator showing the attachment and the
concentric circular glass insert within the iron shell. (Smithsonian
Institution)
Photo Copyright © 2000 Smithsonian Institution -
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Unless otherwise noted, photos by John and Carol McDougald
HOUSE PRINTING TELEGRAPH p.5 of book