172 LETTER TO GORDON. 



the bed of the sea, it only produces an additional expenditure 

 of cable. With equilibrium of the force K the cable settles 

 down in the diagonal of the parellelopiped, instead of in the 

 diagonal of the parallelogram, and the cable -length bears the 

 same proportion to the distance traversed as the -diagonal of 

 the parallelepiped, whose sides are the ship's motion, the depth 

 of water, and the simultaneous velocity of current, bears to the 

 ship's motion. Very violent action on a tightly laid cable may 

 however be exerted by variable currents, as the cable has 

 then to resist the pressure of the water in the form of the 

 catenary curve. Lastly the rising and falling, as well as the 

 lateral movements of the ship, form forces of importance, 

 threatening the fracture of the cable, unless the uncoiling 

 apparatus is very light, or a compensation can be effected, 

 whereby the cable may be lengthened or shortened behind 

 the brake, so that no acceleration of the mass takes place. 

 The mechanism which I propose for determining and regulating 

 the tractive force exerted on the cable is easily calculated 

 as under. (Figure 3.) 



A r -sin= ; K=^ -. 

 ? sm 



k 



sin = ; 

 ah 



Fig. 3. 



I have asked Loffler to calculate a table in accordance 

 with this formula, of which however I am not yet in possession, 

 as L. is still in Cologne, e was, as you state, 25 feet, i. e. 

 842 metres. The weight Q was 160 kilograms, according to 

 the statement of Newall's people, who weighed it. You seem 

 in your approximative formula to have taken pounds instead, 

 your values are therefore only about half those I have in my 

 memory. The apparatus was constructed of wood the evening 

 before the laying. Previously Mr. Liddel seemed not to be in 

 favour of it, and I did not wish to obtrude myself after having 



