ee 
‘LENZ ON ELECTRO-MAGNETISM. 611 
would necessarily increase the force of the electrical current, I there- 
fore made the following experiment. I wound round the armature ten 
convolutions of copper wire bespun with silk, and the conducting wires 
were connected with the ends of this spiral only by asingle twist of the 
wires; the result of the four readings off amounted to 36°8; upon this 
the same connection was made by twisting the ends of the wires ten 
times round one another as tightly as possible; the deviation amounted 
again to 36°8 ; I finally pressed the last connection as tightly as pos- 
sible together with a pair of pinchers, so that they were very much 
flattened ; the deviation was 36°75. We may therefore consider the 
connection made by tightly twisting the wires ten times round one 
another as quite sufficient, and this was therefore made use of in all the 
subsequent experiments. The places where the connection was made 
were then wound round with silk stuff in order to secure them from 
reciprocal contact. 
The second preparatory experiment I made in order to see whether, 
when I advanced the electromotive spiral on the armature more to the 
north limb or to the south limb of the magnet, it had any influence on 
the electric current. For this purpose I obtained with two convolu- 
tions the following results : 
The convolutions advanced till in contact with the north limb 
of the magnet, gave a deviation . . - ie St BPS 
The convolutions advanced until in contact ith the south limb 
of the magnet, gave a deviation . . 2 ap oro 
The convolutions advanced to the middle of both ae gave a 
deviation Dee a tena of eee OU 
therefore this influence also of the different ne of the spirals on 
the armature is imperceptible: from this time I always placed them so 
that the spirals occupied the middle of the armature. 
I thirdly determined, before I proceeded to the proposed experiments, 
the thickness of the copper wires employed; I weighed two feet of 
each having wound off the silk, by which I obtained the proportions of 
their diameter on which it principally depended ; but in order to ob- 
tain also their absolute thickness, I measured the thickest by means of 
amicrometrical contrivance : I obtained the following results, in which 
I have designated the wires, beginning with the thinnest, Nos. 1, 2, 3, 
and 4. 
grains inch. 
2 feet of wire No. 1 weighed = 23°3; absolute thickness = 0-023 
ee ANOS a =) DT Aye 105095 
(wire of the multiplier) 
No. 3 weighed = 83:9; absolute thickness = 0:044 
2—— —__ No, 4 - = 1661; ——____——__—__ = 0061 
All the four kinds of wires were well covered with silk, so that no 
- Vor. I.— Parr IV. Der 
