WILLIAM SIEMENS, F.K.S. 



into the differential equation, we obtain : 



2 7 

 d t = jr- .x(l-x)dx 



Z.rMog. v 'X 



27 r 1 



t=- - I X(l-x}dx 



f.r-log^xy 



.r*kg^ 



. 7./ 

 t 



3 r a X . log - 

 r 



DESCRIPTION OF A MACHINE FOR COVERING 

 TELEGRAPH WIRES WITH INDIA-RUBBER. 



By MR. C. WILLIAM SIEMENS, of London.* 



A SUBMARINE telegraph cable is composed of three essential 

 parts : 1st, the conductor, which generally consists of a strand 

 of seven copper wires twisted together, to give it strength and 

 pliability ; 2nd, the insulating coating, which consists almost 

 without exception of several coatings of gutta-percha put on while 

 hot and in a semi-fluid state by means of piston and cylinder 

 machines analogous to the presses used for making lead pipes, 

 with intervening coatings of a bituminous compound, called Chat- 

 terton's mixture, to establish a more intimate union of the diffe- 

 rent layers of gutta-percha ; 3rd, the sheathing, which is added to 

 protect the insulated conductor and to give strength to the cable, 

 and consists generally of a hemp serving and a spiral covering of 

 iron or steel wire. 



Respecting the conductor, it is important that it should consist 



* Excerpt Minutes of Proceedings of the Institution of Mechanical Engineers, 

 1860, pp. 137-146. 



VOL. II. F 



