118 J. Trowbridge on a new form of Galvanometer. 
Art. XVI—A New Form of Galvanometer ; by Joun Trow- 
BRIDGE, Assistant Professor of Physics, Harvard College. 
of I=tan 9, or = sec?S. When the ratio of the length of 
the needle to the diameter of the coil is a very small fraction, 
the tangents, however, are closely proportional to the corres- 
ponding intensities. 
In Gaugain’s galvanometer 
where the plane of the cur 
rent is placed at a short dis 
tance from the axis of the 
needle, the intensities are di 
ne ae 
this position the needle is un 
sg affected by the current, and 1s 
acted upon merely by the earth’s magnetism. We now turn t 
plane of the current about a horizontal axis passing through 
_ the center of the needle as in the figure; A B representing the 
