104 
THE TELEGRAPH. 
cable consisted of four copper conductors # 06 in. diameter, each 
of which was coated with two separate layers of gutta-percha, 
which brought up the diameter to \ inch. The four conduct¬ 
ing wires were twisted spirally, and the whole was wrapped in 
hemp steeped in tar and tallow. The cable, so formed, is pro- 
^ C 
Fig. 40. 
tected by ten iron wires, each of \ in. diameter, wound spirally 
round it, thus bringing the external diameter up to If inch. 
This cable, 25f miles in length, weighs seven tons per nautical 
mile, and is laid at the maximum depth of 180 feet, which is 
nearly the height of the towers of Notre Dame at Paris. x 
This cable has several times been broken by the anchors of 
ships, but on each occasion there was little difficulty in quickly 
repairing it. In 1859, part of it was raised up by Sir Samuel 
