172 Mr. T. T. P. B.Warren on Prof. Fleeming Jenkin's Formula. 



The calculated loss corresponding to one minute is rather 

 more than 1 per cent. (1-0096) ; 



R = -3535 x 1896 x -00995 =9 miUi ° nS < nearl y>' 

 9 x 1896=17,000 millions per nautical mile. 



Mr. Latimer Clark says (Culley's 'Handbook/ p. 231) that 

 the Atlantic cable when laid had a resistance equal to 2437 mil- 

 lions B.A. units per nautical mile, which after 30 minutes' elec- 

 trification rose to 7000 millions. We must therefore consider 

 the cable to have been highly electrified when Mr. Clark's elec- 

 trometer tests were taken. The calculated fall in these tests 

 does not agree so well with the observed fall as may be wished ; 

 for whatever be the interval for t, B will be constant if the 



C 



correct value of — corresponding to the time t be taken. 



Thus, the fall to half tension being 4000 seconds, we find by 

 i C 



formula n=nt, that 1640 seconds are required to fall to 



log- 



three-fourths (Mr. Clark's tests give 1363 seconds) ; 



B= -3535 xlWx -28540 =9 milUonS (near ^' 

 9 X 1896 = 17,000 millions per nautical mile. 

 And in general, whatever may be the amount of electrification 

 given to a core, B will be constant for all values of 



t is the time or intervals in which C falls to c ; for the electrifi- 

 cation given on charging reduces the rate of loss exactly in the 

 same ratio as it increases the resistance. 



The value for p, as written in my modification of this formula, 

 must in the first instance be obtained by experiment; and it 

 must be understood that t is the time for which a core is held 

 free, and that no provision for the time occupied in charging is 

 made without introducing the value corresponding to it for the 

 period of contact. 



When several coils having different rates of loss are joined up, 

 the rate of loss for each in the same unit of time being known, the 



