Electro-Magnetic and Galvanic Experiments. 145 
shewn fig. 3d. The cap O should be strong and if brass 
should be coated with the cement used in attaching it to the 
glass, (that used for nautical machines is best,) the gage may 
be attached to the cap, or enclosed in the receiver. 
The stiff wire, with the valve T and the ball U, may be 
entirely removed; and for it may be substituted a glass 
tube open at both ends cemented into the cock P, and 
G, as ont 
The weig 
Art. XIII.—4 brief account of some Electro-magnetic and 
Galvanic Experiments. By Rosert Hare, M. D. Pro- 
fessor of Chemistry in the University of Pennsylvania. 
Seven hundred feet of copper wire, nearly as thick as a 
knitting needle, were made to encircle the columns of the 
etnre Room. One end of the wire was connected with 
one end of a large calorimotor—the other, terminated in 
a cup of mercury—into this, a wire proceeding from the 
other pole of the calorimotor was introduced. Under these 
circumstances, a magnetic needle placed near the middle of 
the circuit, was powerfully affected—and when the circuit 
was first interrupted, and then re-established by removing 
the wire from the cup, and introducing it again, the influ- 
ence appeared to reach the needle as quickly as if the cir- 
cuit had not exceeded seven inches in extent. The needle 
being allowed to become stationary in the meridian, while 
the circuit was interrupted, and the end of the wire being 
then returned into the mercury, the deviation of the needle, 
and. the contact of the wire with the metal, appeared per- 
Vou. VIL. No, 1. 19 
7. 
