82 Mr. Spitspury on a Single Galvanie Combination. 
scarcely possible, certainly improbable, that all should be simple ; 
and the time is perhaps not very far distant, when our views m 
reference to these bodies will be very considerably modified. 
To discover in what way the above phenomena were produced, 
two brass wires were placed in connexion with the galvanoscope, 
one containing a much greater extent of surface than the other ; 
the fluid medium was common water. Of course no action was 
apparent. A few drops of nitric acid were then dropped on the 
less wire, which instantly shewed evidence of being in a positive 
state to the larger, continuing so until the acid became intimately 
mixed with the water, when it suddenly changed its state, and 
became during the remainder of the experiment negative. This 
proves that the larger wire acts by, in some way, attracting to 
it a greater proportion of acid. 
Such are the facts which Professor Cumming’s invaluable in- 
strument has brought to light. In these experiments, it was always 
necessary to neutralize the earth’s magnetism by acting on the needle 
in the way described by the late Abbé Hauy ; it was also equally 
necessary to see, that the ends of the wires, by which they were 
connected with the galvanoscope, were coated with mercury ; this 
is rather difficult with iron wires, but may be accomplished by 
immersing them first in a solution of sulphate of copper, and 
afterwards in one of nitrate of mercury. As the galvanoscope 
employed by us was from its construction much more delicate 
than the one described by Professor Cumming, a figure of it 
is annexed, (Fig. 3). 
A, A, A, A is the section of an ivory box containing the spiral 
parallelopipedon of wire, a,a,a,a; on the top it is glazed, that 
the motion of the needle may be observed. B, B is a tube also 
of ivory, containing a screw C, which moves easily but without 
shake; to the point D of this screw is cemented a fibre of silk 
drawn from the silk-worm pod, to which is attached the magnetic 
