Hi, A. Rowland—Moagnetie Hffect of Electric Convection. 33 
the current in the circle outside the inductor will be oS and 
inside the area of the inductor -C On the latter is su- 
perposed the convection current equal to +C. Hence the 
- motion of electricity throughout the whole circle is re what it 
would have been had the inductor covered the whole circle. 
In one experiment 2 was about 8. By comparison with the 
other experiments we know that had electric conduction alone 
presence of so many disturbing causes. o effect was dis- 
deflection of the astatic needle as follows. Turning the two 
needles with poles in the same direction and observing the 
number # of vibrations, and then turning them opposite and 
finding the number n’ of vibrations in that position, we shall 
find, when the lower needle is the strongest, 
n?- 4 
n? tn’? — n2 +n? D (1) 
Where X’ and X are the forces on the upper and lower needle 
respectively, 4 the deflection, D the distance of the scale and 
H the horizontal component of the earth's magnetism. As X’ 
and n’ are very small the first term is nearly X—X’. The tor- 
sion of the silk fiber was too small to affect the result, or at 
least was almost eliminated by the method of experiment. 
The electricity was in the first experiment distributed nearly 
uniformly over the dise with the exception of the oe in 
the center and the excess of distribution on the edge. The 
surface density on either side was 
Am. Jour. isi sas! esses. Vou. XV, No. 85.—Jan., 1878, 
