OF WIRES FOR ELECTRICITT. 



319 



Without r at the beginning of 

 any wire < the experiment 



interposed [_ at its end 



With interposed wire 7 feet long 



14, 



21 



. 28 



35 



Angles of deviation. 



3. 4. Average 



85-3 

 85-7 

 52-3 

 38-2; 

 29-7 

 24-3 

 20-9 



89-7 

 89-3 

 52-4. 

 38-1 

 29-8 

 24.-6 

 20-6 



89-7 

 89-8 

 54-5 

 39-6 

 31-5 

 24-8 

 22-0 



1-57 

 ^'5S 



88 



53-4 



39-1 



30-6 



25-8 



20-9 



88-31 

 53-15 

 38-75 

 30-40 

 24-87 

 21-10 



The calculation of the values of the 7th column was performed in the 

 following manner. I took for the unit of the conducting resistance the 

 length of 1 English foot of the wire, from which the five pieces had been 

 cut, and represented the unknown strength of the current correspond- 

 ing to this resistance hjpi/: and I assumed a; for the equally unknown 

 conducting resistances of the wire of the multiplier and the electromotive 

 spiral taken together. Assuming the hypothesis that the resistances 

 of the wires are proportional to their lengths, and designating the devia- 

 tions observed in the above table for the resistances x, x -\- 7, x + 14!, 

 &c. by a^, a^ ^ j, a^^^^, &c. we shall find, by means of the formulae 

 given in the former Memoir, the following equations : 

 A 



^=^-sin(l«J 



A 



x+ 7 



j; + 14 ^ V^ ■'^+I4y 



&c. 



Dividing the rest of the equations by the first, and designating the values 

 sin {\a^), sin {\ a^ ^ ^), sin (l a^ ^ j^), &c. for brevity sake by a, a', 

 a", &c. we shall obtain 



a; = — ; and therefore ax — i/ = 



a' X —y-\- 7 a' = 

 a"cc-y + 14 a" = 0, 



(A) 



&c. 



