Masterpieces of Science 



much resembles that of its predecessor in 1866. 

 Its exterior armour of steel wires is much more 

 elaborate. The first part of Fig. 59 shows the 

 details of manufacture: the central copper core 

 is covered with gutta-percha, then with jute, 

 upon which the steel wires are spirally wound, 



Fig. 59. Commercial cable, 1894 



followed by a strong outer covering. For the 

 greatest depths at sea, type A is employed for a 

 total length of 1,420 miles; the diameter of this 

 part of the cable is seven-eighths of an inch. As 

 the water lessens in depth the sheathing in- 

 creases in size until the diameter of the cable 

 becomes one and one-sixteenth inches for 152 

 miles, as type B. The cable now undergoes a 

 third enlargement, and then its fourth and last 

 48 



