David Brooks was an American inventor from Philadelphia, Pennsylvania, remembered for an innovative insulator for telegraph lines in 1864 and 1867.
[1] The insulator had a thick metal casing around blown glass; the assembly was held together with molten sulfur.
Out of the tube extends a "ramshorn" rod that held the telegraph wires.
It was mounted into holes drilled into the bottom of wooden crossarms attached to poles.
Prior to the invention, Brooks worked for the Pennsylvania Railroad, which in the 1850s received permission to build its own telegraph line, having bought necessary patents.