Measure of Resistance to Galvanic Currents. 27 
whence, integrating with respect to z, 
alge dz l Ste 
w={ (Rr) 2? (R—r)r (-- 3) 
or l 
ee as ne te egal on a 
If, now, V be the volume of the truncated cone, G the weight 
of the mercury contained in it, and o its specific gravity, then 
V=(R?+Rr+7?) = 
3 ; 
and dividing both sides by Rr, we have 
Vv R +]+ Z ) i : 
Rr r Heo * 
Bret Sg 
or calling 72 Re bor, ae i 
EU ae; aati) an 
whence 71 es NE 3 
and putting for V its value = 
ip ss 2 
lire ‘s ig 
Peat 
which, substituted in equation (1), gives 
Thee RS lle eating daiat) 
The value of W found from this equation is obviously correct 
for every conductor of pyramidical form, as long as a represents 
the ratio of the greatest and least sections. It is moreover 
equally true when, instead of a single truncated cone of length 
/, any number of equal cones be substituted whose collective 
length is J, provided only that in each the ratio of the greatest to 
the least section, or its reciprocal, is a. , 
For in this case, if 
. l=" 
where A is the length of one of the cones, 
