244 APPLIED SCIENCE 



Bright and Clark for the Indian Government, under the super- 

 intendence of Colonel Stewart, was thus covered. The excellence 

 of this cable, 1,176 miles long, laid near Kurrachee, in a sea with 

 the temperature at the bottom of 24- 2 C., and at the top of 26 

 C., is a proof that gutta-percha may, with due precaution, be 

 used in tropical climates. 



The gutta-percha resistance per mile of this cable varies 

 from 575 to 268 millions of British Association units per mile, 

 according to the temperature at the bottom in the various sec- 

 tions. It was laid from sailing vessels towed by a steamer. The 

 diameter of the main cable, covered with compound, is 1 

 inch, and its weight is about 3'7 tons per mile. The Lowestoft- 

 Norderney Cable, 240 miles long, laid in September last, from 

 England to what was Hanover, is the heaviest, on the whole, 

 yet laid. It weighs 10^ tons per mile, is 2 inches in diameter, 

 contains four insulated conductors, is covered with Bright and 

 Clark's Compound, and would bear a strain of twenty tons. It 

 has twenty miles of shore end, each mile of which weighs twenty 

 tons, and would bear a strain of forty tons. The insulation re- 

 sistance of each mile, as it lies in the North Sea, is 1,100 millions 

 of British Association units, and the four wires are remarkably 

 uniform. This cable was laid for Messrs. Renter's Telegram 

 Company, under the superintendence of Messrs. Forde and 

 Fleeming Jenkin. The contract was let to the Telegraph Con- 

 struction Company, and the cable made and laid by Mr. Henley. 

 The England-Holland Cables are shorter examples of equally 

 colossal proportions. There are now seven cables at work 

 between England and the Continent, and three between England 

 and Ireland. The Malta-Alexandria Cable, 1,330 miles long, 

 laid for Government in 1861, under Mr. Forde's superintend- 

 ence, by Messrs. Glass, Elliot and Co., also deserves mention. 

 Although not designed for shallow water it has done good 

 service ; but the frequent interruptions which occur will serve 

 as a warning not again to use a cable weighing less than two 

 tons per mile in shallow seas. Those who wish for fuller 

 information concerning the less important lines may consult 

 the references given in the course of this article. The most 

 important fact to be stated about shallow sea lines is that 

 the Dover-Calais Cable, laid sixteen years ago, is still working, 

 and likely to continue to work for many years to come. 



