LINES OF MAGNETIC FORCE — DEFINITE FORCE OF A MAGNET. 
153 
contained 7*25 inches in length of copper wire 0-1 of an inch in diameter, and was of 
course employed in all the following comparative experiments ; the distance of the 
loop and magnets from the galvanometer was 9 feet. For one passage over the pole 
either on or off, i. e. for one intersection of the lines of force of the magnet D, the 
galvanometer deflection was 8°'36. For one intersection of the lines of force of the 
other bar E, the deflection was 8°'78. The two bars were then placed side by side 
with like poles together, and afterwards used as one magnet ; their conjoined power 
was 16®*3, being only 0°'84 less than the sum of the powers of the two when estimated 
separately. This indicates that the component magnets do affect, and in this position 
reduce, each other somewhat ; but it also shows how small the effect is as compared 
with ordinary magnets (3222.). 
3218. The compound magnet DE (3217.) was now subjected to the close action of 
another magnet, sometimes under adverse, and at other times under favourable con- 
ditions ; and was examined by the loop as to the sum of its power (not the direction) 
under these circumstances. For this purpose it was fixed, and another magnet A 
brought near, and at times in contact with it, in the positions indicated by the figure 
8 ; the loop in each case being 
applied many times to D E, 
that a correct average of its 
power might be procured. The 
dominant magnet A was much ^ uj 
the stronger of the two, having 
the power indicated by a swing 
deflection of 25°74. 
3219. When the relative position of the magnets was as at 1, then the power of 
DEwas 16°"37 ; when as at 2, the power was 16°-4; when as at 3, it was 18°75; 
and when as at 4, it was 17°‘18. All these positions are such as would tend to raise, 
by induction, the power of the magnet D E, and they do raise it above its first value, 
which was 16°'3 ; but it is seen at once how little the first and second positions ele- 
vate it ; and even the third, which presents the most favourable conditions, only in- 
creases the povver 2°*45, which falls again in the fourth position. 
3220. Then the dominant magnet A was placed in the same positions, but with the 
ends reversed, so as to exert an adverse or depressing influence; and now the results 
with D E were as follows ; — 
Position 1 15*37 
Position 2 15*68 
Position 3 15*37 
Position 4 16*06 
All these are a little below the original force of D E, or 16°*3, as they ought to be, 
and show how slightly this hard bar-magnet is affected. 
MDCCCLII. X 
