Intelligence and Miscellaneous Articles. 315 
with a force which exceeds the estimated amount by 4°7 grains, 
whereas the soft iron needle, under the same current force, falls 
short of the calculated amount by 11°4 grains. The last effect is 
probably attributable to the fact that, as the needle approaches satu- 
ration, the law of the squares gradually merges into the law of 
simple proportion. ‘The writer regrets that he had not at com- 
mand sufficient battery power to put this point to the test of decisive 
experiments, but hopes to do so shortly with a Daniell battery of 50 
or 100 elements. In the meantime the results above given, having 
been arrived at with great care, and amply confirmed by experiments 
several times repeated, appear to establish very conclusively the 
following principles :— 
1. A permanently magnetized steel needle, suspended in the 
middle of a galvanometer coil, is deflected with a force simply pro- 
portional to the quantity of current transmitted, so long as the 
current force which acts upon it is not sufficient to impart tempo- 
rarily a higher magnetism than that which it permanently possesses. 
Beyond this point, the deflective force exerted on the magnetized 
steel needle increases in a somewhat higher ratio than the current, 
and therefore the accuracy of any form of galvanometer can be 
trusted only within certain limits of current force and of length and 
proximity of coil. 
2. A pure soft iron needle, suspended at an angle of about 40° to 
the direction of the current (the angle varying according to the 
shape of the needle), is deflected with a force which, within certain 
limits of current power, is very exactly proportional to the squares 
of the quantities of current. Beyond these limits the deflective force 
exerted on the needle increases in some constantly diminishing ratio 
lower than that of the squares of the current. 
3. The action of the current in deflecting a magnetic needle is 
precisely the same action, and follows the same law, as that which 
it exerts in magnetizing a bar of soft iron. The amount of magnetism 
actually imparted to a bar or needle of soft iron is directly propor- 
tional to the quantity of current; for the force with which a soft iron 
needle is deflected under different currents is not proportional to its 
temporary magnetism in each case, but to the product of its mag- 
netism multiplied by the force of the current. By increasing the 
force of the current, two effects are produced ; in the first place, the 
magnetism of the needle is increased in the same proportion; and 
secondly, the increased current acting upon this increased magnetism 
deflects the needle with a force proportional to the product of the 
two, or in other words, proportional to the square of the actual 
quantity of current. 
1t only remains to add the results of two series of experiments, 
showing the very striking difference between the defiective forces 
exerted upon the two needles at different angles of inclination. 
Table III. shows the increasing weights required to balance the 
needles at angles successively diminished by 10°; Table LV. exhibits 
the effect produced by successive additions of weights, equivalent to 
a force of ten grains acting at the poles of the needles. In both 
