Intelligence and Miscellaneous Articles. 313 
the balance galvanometer back to zero; the fifth column expresses 
the same weight reduced to the force which it exerts at the poles of 
the needle, but increased in each case by half a grain, to compensate 
for the small preponderance given to the long arm of the lever 
in order to keep the needle vertical when not deflected by the 
current ;— 
Table I. 
1 . 2. a 4 . 5 . 6 . 
Angles on Angles on Weights Force at “at 
No. of tangent balance Fi ieee to bring poles of Raped 
pairs. galvya- galvanometer, the needle to needle, in nadiieedl 
nometer, without weight. zero. grains, 5 
Le] ! ° / 
1 4 30 66 100 grs. at 2°5 3°00 3°12 
2 8 30 77 30 ” ” 5°5 6:00 5°96 
6 29 30 87 1000 grs. at 2°2 22°50 22°64 
12 44 45 89 ” 5 4°9 49°50 39°64 
It will be seen that, up to six pairs, the numbers in the fifth column, 
expressing the force of the current in grains at the poles of the needle, 
vary very nearly in the same ratio as the tangents of the angles of 
deflection on the tangent galvanometer reduced to a comparable form 
in the sixth column. With twelve pairs, however, the weight re- 
quired to balance the current is 49°5, or very nearly 50 grains; 
whereas, according to the tangent galvanometer, it should not have 
exceeded 40 grains. Reflecting on this anomaly, the writer could 
only arrive at the conclusion that the needle, surrounded by a very 
powerful current in such a large coil, ceased to act as a permanent 
magnet, and was temporarily charged with a higher magnetism in- 
duced by the current itself. Subsequent experiments completely 
confirmed this conclusion; and he was led to examine the subject 
more minutely by observing that the needle, after being several times 
subjected to the action of the current from twelve pairs, appeared to 
have lost its permanent magnetism; for he afterwards found re- 
peatedly that when the index was brought back by successive 
increments of weight to 40°, the smallest possible additional weight 
sent it back to zero. Before taking out the needle to ascertain 
this, he submitted it a second time to the action of six and twelve 
pairs, with the following results :— 
Number of pairs. Current force by tang. galvan. Weights supported. 
6 22°64 7'5 grains, 
12 39°64 24°5 i, 
whereas it will be seen, by referring to the preceding Table, that 
originally it supported 22°50 and 49°50 grains respectively. The 
needle was then taken out, and was found to have almost entirely 
