624 LENZ ON ELECTRO-MAGNETISM. 
all ; 
x= (L+3, 2) psn. bal 
ql 
v= (L + aan) P sin. 5. a!", 
consequently, by division, 
L+a  sin.ta sin. 4 a 
Mae sin. da! o b+ =(L+ Lene 
ml 
_ L+a sin.La sin.ta 
A tig A ° sin cue or L4+— n= (L + A) ane al 
lope ali “2 ee 
—- sin. La sin. £ 
1 = oe : i Lal” or L+ 5, =(L+ Aaya TCU 
mil! 
from which equations m!, m!, and m'"' may be found. 
For our case, Lis = 849 inches, A = 84°1, a = 21° 52', a! = 17° 36, 
a!’ = 15° 34", a!!! = 18° 20, hence we have 
Capacity of conduction of copper ......... = 1°00000, 
a ee eee iron or m’...... = 0°27321, 
——_—___—_—_—— platina or m’ =0:18370, 
a brass or m!"’... = 0°32106. 
We might still find these values more exactly if the lengths of the 
wires were greater ; but this investigation did not properly come within 
the scope of this paper, I therefore defer it till another occasion. 
Consequences of the Laws already established in respect to the Con- 
struction of Electromotive Spirals. 
In the following experiments I suppose the magnet for the produc- 
tion of the electric current to be given here, therefore the question is 
to determine those spirals of a certain metal which act most advan- 
tageously with this magnet and its cylindrical armature, which is like- 
wise given. Further, I suppose the spirals, together with their free, 
not wound ends, to consist of one and the same wire; moreover, it is 
self-evident that every other property of the ends of the wires not be- 
longing to the electromotive spirals may be reduced to those above men- 
tioned, if we know the length, the diagonal, and the conducting power 
of the pieces of wire brought into the circle. 
It is easy to see that by increasing the convolutions ad infinitum we 
do not also increase the strengths of the current ad infinitum. In the 
first place,—the number of convolutions of a given wire is limited by 
