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Electrical
Insulators: Samuel
Morse invented the electromagnetic telegraph in 1832. The glass
insulator for telegraph wire was invented by Ezra Cornell in 1844.
Another use for insulators came with the invention of the telephone in
1876 by Alexander Graham Bell. One
area of the United States is no better than another for finding
insulators since there were many sizable population centers on the West
Coast as well as the East by the late 1870’s. In
the early 1870’s, telephone wires were merely strung between house
tops. As the use of the telephone grew, so did the problem of finding
room to put the wires and insulators. In the 1880’s, telephone poles
were employed in cities to organize the wire. In the older sections of
cities that date to this era, the glint of an insulator under the roof
eaves of a house can still be seen. Before
1865, insulators were made without internal threads. They were simply
forced onto pegs or glued in place. In 1865, Louis Cauvet patented
patented the threading of insulators for mounting on threaded pegs. Although
it is too lengthy an explanation to tell in an article, an example of
dating insulators in given. One particular brand that can be accurately
dates in that of the Brookfield Company. The earliest Brookfields were
embossed on the dome rather than on the skirt, and can be dated by the
address that appears on the dome. From 1868 to 1882, the address was 55
Fulton Street, from 1882 to 1890 the address was 45 Cliff Street and
from 1890 to 1897 the address was 80 Fulton Street. As
more complex problems developed with the growing industry, new types of
insulators were invented. Rain, which would short out the wire, was
taken care of by a new addition to insulators called drip points. The
drip points helped the rain to drip off the skirt of the insulator.
These little points of glass on the skirt were sharp but broke off
easily and were replaced with round drip points. They were patented in
1893. Most
insulators were made of glass or ceramic. Some companies actually melted
down old bottles as a source of glass for their molds. The natural color
of glass ranges from blue to green. Many insulators were made in
different colors so that linemen could visually trace a wire over a long
distance on a cross arm that had many different wires on it. Some early
insulators such as the E.C.& M. of San Francisco (made in the
1870’s) were made in a two piece mold. The seam can be seen all the
way around the insulator with a little glass blob on the side. The blob
was left where the molten glass was poured into the mold. Just
like coins, insulators have misspellings and over prints. Many have been
cataloged but new ones are still being found. A scarce and uncatalogued
embossing error can make it an extremely valuable insulator. In
the last 20 years, insulator collecting has grown into an international
hobby and many insulators have become very valuable. When you’re out
for a drive on the weekend, looking for a good place to coin shoot with
your metal detector, don’t forget to keep your eye out for the
telltale glint of glass that may be a valuable insulator.
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