46 REPORT—1849. 
5. The plates may be placed at the sixteenth of an inch, and even less, apart: an 
enormous acting surface may thus be obtained in a very small space, and an additional 
strength of galvanic current, owing to the nearness of the plates. 
6. There is no danger of the boiling of the solution. 
7. The plates once arranged in a suitable framing would not require to be disturbed 
for a very considerable period. 
Since the above was written, further experiments have been made, in order to 
simplify the method of preparing the zinc plates, and the following is the method 
which appears the best : ; 
After the plates are cleaned with emery, immersion in dilute sulphuric acid, and 
then in water, they are dipped into a mixture of about equal parts by measure of 
saturated solutions of chloride of mercury (corrosive sublimate) and acetate of lead ; 
they are then rubbed with a cloth and washed, and are ready for use. 
The superiority of this method of preparing the plates consists in the fact, that 
local action is entirely prevented, and they only require one preparation until they 
are quite dissolved ; they are not so liable to break as common amalgamated plates 
are, and are therefore able to be used as long as any metal remains. 
They are also more highly positive than common amalgamated zinc plates, 

On Motions exhibited by Metals under the Influence of Magnetic and Dia- 
magnetic Forces. By W.Syxes Warp. 
In the course of a series of experiments in relation to diamagnetism, I observed 
that the nature of the action upon many metals varied with the intensity of the mag- 
netic force; and I found that such effects were in accordance with the observations 
of Prof. Plucker, ‘‘that the diamagnetic force increases more rapidly than the mag- 
netic in relation to the power of the exciting magnet.” [ took considerable care in 
procuring specimens of pure silver, copper, lead, tin and zinc, and found that these 
assumed the magnetic or diamagnetic state according to the power of the magnet 
employed. I found a magnet of very moderate size and power sufficient if the polar 
pieces were brought near to eacl: other, and the metals, the subject of experiment, 
were in small discs and delicately suspended. 
My attention being particularly directed to the phenomena which Dr. Faraday 
terms revulsion, I observed that the direction of the revulsive motions changed when 
the magnetic or diamagnetic state of the metal was changed. 
When the polar pieces were adjusted within one quarter of an inch apart, and the 
disc of metal so suspended that one-half was without, and the other half between the 
polar pieces, another series of phenomena presented themselves. On developing 
the magnetic force, the disc moves as a pendulum, with a tendency to pass outwards 
from between the polar pieces; on breaking contact, the disc moved in the reverse 
direction, tending to pass within the polar pieces. Such motions are remarkable, in 
that the direction of them is alike in all metals. Such motions appear to result 
from electrical currents rather than from magnetic or diamagnetic forces; for on sub- 
stituting for the disc of metal a flat spiral of insulated wire, they were not produced ; 
but on using a similar spiral, but of which the ends of wire were in good contact, 
the like phenomena were observed as with a disc. 

On a Theory of Induced Electric Currents, suggested by Diamagnetic Phe- 
nomena. By W. Syxes Warp. 
The phznomena mentioned in the foregoing paper involve many points which 
cannct be easily accounted for according to the received theories of magnetism. 
Ampére’s theory may account for magnetic or diamagnetic phenomena taken sepa- 
rately, but not easily for the changes of condition which take place in the same metal, 
still less for the changes in the direction of the revulsive motions, particularly those 
which follow the sluggish condition of the metal under the influence of that amount 
of force by which the magnetism or diamagnetism are nearly balanced. 
It also appears that the induced or secondary electric current may be accounted 
for on the hypothesis that the current in the primary conductor effects a molecular 

