I meant to post these images with my first insulator post to provide a visual example of how the glass insulator was utilized on telegraph lines. I took these pictures on a brilliantly clear fall day while riding the Richland County B & O rail trail. I estimate these poles to be around 40 or 50 years old and they have certainly seen better days. These poles have the more modern steel pins that the insulators screws onto. Older lines used threaded wooden pins while the very first teleghraph lines used smooth pins. Early threadless insulators were glued to the pin with pine pitch. In the northern parts of the country freezing temperatures would cause the pitch to contract and the insulator would pop loose from the pin requiring constant repair.
A threaded system of attachment was invented by Louis A. Cauvet and a patent was granted on July 25, 1865. The Brookfield Company of New York liked this idea and bought the patent. It is likely that the first insulators with internal threads were made by Brookfield. The threaded system was a success and is still in use today 145 years later.