90 THE SCIENTIFIC PAPERS OF 



two precipices, involving great danger of rupture, which actually 

 did take place shortly after the cable had been successfully laid. 

 In cases where such gulfs were known to exist, the only safe plan 

 was to stop the ship, and allow the cable to run out so as to furnish 

 enough to lie on the bottom at every point, however deep. This 

 was a serious source of danger, against which it was important 

 that every precaution should be taken. Deep sea soundings were 

 not generally taken at sufficiently frequent intervals, and cables 

 were seldom laid in the line of soundings. 



ON THE ELECTEICAL TESTS EMPLOYED DURING 

 THE CONSTRUCTION OF THE MALTA AND 

 ALEXANDRIA TELEGRAPH, and 



ON INSULATING AND PROTECTING SUBMARINE 

 CABLES. 



BY CHARLES WILLIAM SIEMENS,* M. Inst. C.E. 



THE subject of submarine telegraphs having been fully discussed 

 at this Institution during the last session,! the author feels some 

 hesitation in again introducing it. But several important cir- 

 cumstances have arisen since then, which render its further con- 

 sideration desirable. The publication of the " Report of the Joint 

 Committee on the Construction of Submarine Telegraph Cables " 

 has disembarrassed the question of much uncertainty, by providing 

 an impartial and complete record of the principal facts in connec- 

 tion with past experience. The experimental researches under- 

 taken on behalf of that committee have also added considerably to 

 the stock of theoretical information, which was wanting to form a 

 secure basis for further progress ; and the successful completion of 

 the Malta and Alexandria telegraph cable is another important 



* Excerpt Minutes of Proceedings of the Institution of Engineers, vol. xxi., 

 Session 1861-62, pp. 515-530. 



f Vide Minutes of Proceedings Inst. C.E., vol. xx., pp. 26-106. 



