314 Intelligence and Miscellaneous Articles. 
lost its magnetism. It had originally lifted 44 grains; it was 
now only with the greatest precaution that it lifted 2 grains. But 
7°5 > 24°5 
and (22°64) : (39°64)? 
A ef 
bs, 3:06. 
The writer had therefore little doubt that, if not merely demagnetized, 
but formed of soft iron, the needle, when placed in a favourable 
position, would turn with a force proportional to the square of the 
current ; whereas it plainly appears from Table I., that so long as its 
permanent magnetism is sufficient to resist the inducing action of 
the current, the needle is deflected with a force simply proportional 
to the current. 
To determine this interesting question, two new needles were con- 
structed, similar in shape and size to the former, but somewhat 
lighter, each weighing only 17°25 grains. ‘The one was of steel, 
tempered to the hardness of glass; and was magnetized till it lifted 
with some difficulty 43 grains; the other was of soft hoop-iron, 
well annealed. With these needles the following results were 
obtained from experiments conducted very carefully, and using, for 
greater accuracy, a single-thread suspension :— 
Table II. 
a 2. 3. 4. 5. 6. 
Angles on a Deflective a "a . 
| No, of tangent Tangents to force at poles | Ratioof Ratio pt 
pairs. galvano- rad. 1. of needle, in | tangents. pee eee ss * 
meter. grains. craps? Bo 
With |( 3 | 17 40 0-318 115 115 | 114 
magnetized, 6 31 20 0-609 22°0 22°0 42°1 
steel 9 41 0 0°869 32°5 315 85°8 
needle. | 12 | 47 0 1-072 43°5 38°8 130°6 
| 3| 1740 | 0-318 60 | 60 | 60 
With needle | OE asi 0 0-601 20°5 Le eee 21°5 
of soft iron |) 9 40 20 0-849 400 | 161 42-9 
12 47 0 1°072 57:0 20°4 68°4 
A glance at the above Table will show that, with the permanently 
magnetized needle, the numbers in column 4, expressing the de- 
flective force of the current in grains, are very nearly proportional 
to the numbers in column 5, expressing the simple ratio of the tangents 
or quantities of current; whereas with the soft iron needle they are 
nearly proportional to the sguares of the same quantities, reduced to 
a comparable form in column 6. In both cases the only marked de- 
viation coincides with the powerful current from twelve elements of 
the battery, in which cuse the steel needle, evidently acting under 
the superadded influence of induced temporary magnetism, is deflected 
