122 
cast after being melted in an iron ladle; nevertheless they 
were decidedly dia-magnetic, even with very slight powers, 
and with the polar pieces distant : thus negativing the 
supposed need for great care to insure perfect freedom 
from iron, at least as regards these metals. Mercury was 
also found dia-magnetic under any power which would at 
all affect it in this respect. It did not distinctly exhibit 
any revulsion. Of arsenic I had not such a specimen as 
enables me to speak decidedly. It appeared to be mag- 
netic with the poles distant, dia-magnetic with the poles 
close. The structure was so decidedly crystalline that I 
could not ascertain whether the change of position was not 
due to the varying ratio of the magne-crystallic force. 
The four last mentioned metals did not show any decided 
revulsion when the circuit was broken, but if any took 
place it was that of attraction, but it was too slight to be 
relied on ; for the dia-magnetic action so repelled the body 
from the adjacent pole, that when such action ceased, the 
disc under trial would swing as a pendulum, under the 
mere action of gravitation. On very careful examination, 
however, it appeared that the motion, under such circum- 
stances, was somewhat quicker than was due to gravitation 
alone. 
The specimen of zinc which I selected for the purpose 
of these experiments was reputed pure, having been pre- 
pared for use in Marsh's apparatus, and had not been 
hammered or rolled. It was much less magnetic than other 
specimens of the ordinary sheet zinc. The polar pieces 
being adjusted at a distance of three quarters of an inch, 
(0.75,) the piece of zinc was attracted when contact was first 
made, and afterwards appeared sluggishly to retain any 
position in which it might be placed, but, nevertheless, 
slowly moved to the equatorial position ; that is, it appeared 
magnetic at the first contact, but afterwards gradually 
