106 Deeh Sea Telegraph Cables. 
after submergence, and always insuring a continuous action 
of electric conductibility. 
Allan’s cable, that he proposed to apply in pee of the 
new Atlantic, which is 1 1I-10th of an inch diameter, 
with a specific gravity of 19, weighing 31 cwts. per 
nautical mile in ship, and 14} in sea, now submerged 
between Ireland and Newfoundland by the Telegraph 
Construction and Maintenance Company, being only 3 of 
an inch diameter, with a specific gravity of 1°5, weighing 
but 84 cwts. per nautical mile in ship, and 24 in sea, con- 
tains the same amount of conductibility. The weight of 
the 2,000 nautical miles laid, being then reduced to 
850 tons instead of 3,100 tons, shows a clear saving of 
2,250 tons, and no less than £200,000 in the construction 
alone. 
Its combined conducting power consists of a_ solid 
copper wire, weighing 250 lbs. per nautical mile, closely 
surrounded and shielded with the full strength bearing of 
20 No. 24 best steel wires spirally enclosing it. The 
3-16ths of an inch (No. 9 gauge) metallic rope, or zuerten- 
sible core, thus formed, constitutes the integral strength of 
the cable. When wrapped in insulating substance (four 
coats of gutta percha, alternated with four thin layers of 
compound, weighing 400 lbs. per nautical mile) firmly 
bound, and covered externally with protective coating of 
hemp canvass, thus completing Allan’s 2 cable without 
exceeding 84 cwts. per nautical mile, it is so strong, and 
yet so flexible, that it will resist, without elongating even 
I per cent., upwards of 54 times more strain than the new 
Atlantic cable. 
As has been above partly stated, the reasons are :— 
That, as in all the submarine cables which have failed, 
the conductor, or core, which in the new Atlantic cable 
consists of a strand of seven No. 18 copper wires set 
together, weighing 300 lbs. per nautical mile, equivalent to 
No. 9 gauge, is not strengthened previous to its insulation, 
which is exactly of same materials and weight as in Allan’s. 
And that, to the outside of the insulator only, is applied 
material weight, which certainly affords some resting 
support, but very little direct strength to the part of the 
cable which ought to be made sufficiently strong. 
In the new Atlantic cable, the insulated conductor is — 
wrapped in a layer of jute yarn, and enclosed in a padding 
made of ten No. 13 galvanized iron wires, surrounded with _ 
untatred Manilla yarn, spirally wound, intended to afford — 
