418 <A. M. Mayer—New form of Lantern-Galvanometer, 
A coil of 20 inches in diameter formed of one turn of ;', inch 
wire was rotated 180° around a vertical axis 3} feet from the 
end of the magnet. The needle was deflected 8°. 
Exp. 4. A coil of 20 inches in diameter having 5 turns of 
zz inch wire was rotated 180° around a vertical axis, at a dis- 
tance of 34 feet from end of magnet. Deflection of needle was 
30°. 
Exp. 5. Same as Exp. 4, only coil had 10 turns of wire in- 
stead of 5. Galvanometer needle deflected 50° to 60°. 
Exp. 6. A coil of 20 inches in diameter formed of 10 turns, 
z» inch wire was revolved 180° around a vertical axis 64 feet 
from end of magnet. Deflection of 22°. 
Exp. 7. The coil used in Exp. 6, was placed three feet eight 
inches above center of axis of the magnet and revolved 1 
around a vertical axis; the needle was deflect ‘ 
Exp. 8. A coil of 24 feet in diameter, formed of 40 turns of 
800 feet of ;', inch wire, was placed 28 feet distant from the 
center of the magnet, and with its plane coinciding with the 
plane of the magnet’s equator. On rotating it around a vertr 
cal axis the needle was deflected 20°. 
The following experiments will show the excellent propor 
tions (arrived at by a long series of experiments) of the 
used in Exps. 1,2 and 8, for the evolution and study of the 
electric currents induced by the earth’s magnetism. 
xp. 9. The coil used in Exps. 1, 2 and 8 was laid on a table 
and its terminals connected with a galyanometer, which 1s 
in connection with Nobili’s thermo-electric pile. The me 
of this instrament made one oscillation in nine seconds. 
lifted the east side of the coil only six inches; the needle was 
deflected 10°. Lifting the same side nine inches, the needles 
went to 22°. I now placed the coil in a north and south vert 
cal plane and suddenly tilting its top six inches to the east OF 
to the west the needles went to 60°. Tilting the coil nine 
inches sent the needles with a blow against the stop at ue 
The advantages of the new galvanometer may be summ “ 
in a few words. It gives on the screen a bright clear eee 
only the graduated circle and of the needle. It can read . res 
rendered more or less astatic to adapt it to the character © “8 
electric currents worked with. The direction of its need’ 
completely under the control of the damping — 
finall: , it is of simple construction and can be rapidly a¢j4 
to the requirements of any special experiment. 
