1864. | Farrsarrn on Submarine Telegraph Cables. 625 
the cable was manufactured, one half by Messrs. Glass and Elliott, of 
Greenwich, and the other half by Messrs. Newall and Co., of Newcastle- 
on-Tyne. As one article has already been devoted to the history of this 
ill-fated cable,* we will not further allude to it, than to say that the 
failure of this enterprise may be attributed to the want of care and 
proper supervision in the manufacture, and, to use the words of the 
commission, ‘‘ practical men ought to have known that the cable was 
defective, and to have been aware of the locality of the defects before 
it was laid.’ We might multiply instances of several other similar 
failures, such as the Red Sea and India, the Spezzia and Corsica, and 
the Bona and Cagliari cables, all of which are now useless. 
In deep-sea lines there are three points which require careful con- 
sideration, and which appear essential to success, namely—the tensile 
strength and conducting power of the cable, perfect insulation, and 
machinery calculated to pass the cable with safety from the ship into 
the sea. If this latter can be properly effected, we may venture to 
assert that a well-insulated cable, when once laid, may be retained for 
a series of years in satisfactory working order. 
In the forthcoming Atlantic telegraph, every possible precaution 
has been taken to have a sound and suitable cable in the first instance, 
and Messrs. Glass and Elliott have not only conformed to the recom- 
mendations of the scientific committee, but they have chartered the 
Great Eastern steamship for the exclusive purpose of laying the cable, 
commencing probably at Newfoundland, and continuing the process of 
paying-out, as we hope, without break or interruption, till it is safely 
landed at Valentia. As the construction of the cable is equally im- 
portant with the skill with which it is laid at the bottom of the 
Atlantic, it may be interesting to compare the present cable with those 
previously laid down, and to show with what precaution the directors 
of the company have undertaken this important and precarious task. 
In all the cables we have specified, the same general principles 
prevail, viz. :— 
1. The central conductor is a copper wire, or strand of wires. 
2. The insulating covering is gutta-percha. 
3. The external protection, when used, consists of hemp or other 
fibrous material, impregnated with pitch or some other resinous sub- 
stance, nearly in all cases covered with iron or steel, more in the form 
of an ordinary rope. 
4, The cables so prepared have been paid-out over the stern of 
ordinary vessels, with a pressure-break to regulate the delivery accord- 
ing to the speed of the vessel, which has averaged from four to six 
knots per hour. 
Tn all cases copper has been chosen for the conducting wire, its 
durability and its high conducting power rendering it peculiarly 
applicable for the purpose. In the first telegraphs, the conductor 
generally consisted of a No. 16 copper wire. Thissize gave abundant 
area, and the resistances, even when in lengths of several miles, were 
* <The Atlantic Cable and its Teachings,’ QuarreRLY JOURNAL OF SCIENCE, 
No. 1, p. 44. 
