1864. FainBarrn on Submarine Telegraph Cables. 641 
that which is intended for submersion in 1865. From these will be 
seen the difference of weight and strength, and judging from the pre- 
cautions that are now taken to have the cable retained in water-tanks, 
and carefully tested before immersion, we may reasonably infer that, 
on or before this time next year, a successful and satisfactory tele- 
graphic communication will be permanently established between this 
country and the American continent. 
Fic. 8.—Cuble of 1858. 
Conductor—A copper strand, consisting of 7 wires (6 laid round 1), and 
weighing 107 lbs. per nautical mile. 
Insulator.—Gutta-percha, laid on in three coverings, and weighing 261 Ibs. 
per knot. 
External Protection—18 strands of charcoal iron wire, each strand composed 
of 7 wires (6 laid round 1), laid spirally round the core, which latter was pre- 
viously padded with a serving of hemp saturated with a tar mixture. The separate 
wires were each 22} gauge; the strand complete was No. 14 gauge. 
Weight in Air.—20 ewt. per nautical mile. 
Weight in Water—13°4 ewt. per nautical mile, or equal to 4:85 times its 
weight in water per knot; that is to say, it would bear its own weight in a little 
less than 5 miles depth of water. 
Breaking Strain —3 tons 5 ewt. 
aceuett Water to be Encountered.—2,400 fathoms, or less than 24 nautical miles 
in depth. 
The Contract Strain was equal to 4°85 times its weight per nautical mile in 
water. 
One Knot, being in fathoms = 1,014 x 4 = +9120 = 2-05 times the strength 
requisite for the deepest water. 
Fic. 9.—Cable of 1864-5. 
Conductor —Copper strand, consisting of 7 wires (6 laid round 1), and weigh- 
ing 300 Ibs. per nautical mile, embedded for solidity in Chatterton’s Compound. 
Gauge of single wire, -048 = ordinary 18 gauge. Gauge of strand, :144 = ordinary 
No. 10 gauge. 
Insulation —Guitta-percha, four layers of which are laid on alternately with 
four thin layers of Chatterton’s Compound. The weight of the entire insulation, 
400 Ibs. per nautical mile. Diameter of core, -464; circumference of core, 1-392. 
Bxternal Protection.—10 solid wires of the gauge -095 (No. 13 gauge) drawn 
