Axial Galvanometer. 137 
small brass wire 3, passing through the top board of the frame- . 
work, and attached to the short arm of a bent lever balance, 4. 
The helices are supported upon the shelf 7, which is raised and 
lowered, and sustained by means of the pins 6,6 passing through 
holes in the frame and under a projection from the shelf, which 
slides freely in the slot 5, 5. Fig. 1. 
The wires from the helices 
p,m, are to be connected in 
any suitable manner with 
the poles of a battery. 
Guide-rods or pins may be 
inserted in the poles of the 
magnet, which pins or rods 
may pass through holes in 
the centre of a plate of me- 
tal let into the lower board 
of the stand, or one a little 
more raised, so as to allow 
for the motion of the entire 
length of the bar; but this 
last device is hardly neces- 
sary, for if the bar should 
incur friction by touching 
the helices, it is easily freed 
from it by slightly shaking 
the apparatus. Ihave some- 
times used the spring bal- 
ance instead of the bent 
lever, and although the for- 
mer is not so sensitive as 
the latter, yet it possesses 
some advantages. In the 
bent lever balance, the point of suspension of the wire 3 must 
describe an are of a circle, while in the spring balance the point 
of suspension moves in a straight line, making less liability to 
friction. 
Operation.—W hen an intensity battery, say two or any number 
of Grove’s battery, is connected with the helices by means of the 
extremities p,m, the bar 2,2 is drawn down with a degree of 
force which will be indicated by the scale of the balance. The 
Vol. xxix, No. 1.—April-June, 1845. 18 
CIITA cae 
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