electrical and chemical changes , 399 
early view, which appear to me of the strictest demonstrative 
nature. 
A solution of nitre, which is a substance neutral to the con- 
tact of noble metals, was introduced into a glass cup contain- 
ing a plate of platinum connected with the multiplier ; pure 
concentrated nitric acid was placed in another cup, in which 
there was another plate of platinum joined to the other wire 
of the multiplier, and the connexion was made by a piece of 
asbestus wetted in a solution of nitre. At the moment of 
contact, the needle indicated a strong electrical action, nega- 
tive on the plate plunged in the acid, and which occasioned a 
permanent deviation of about 6o°. 
This arrangement was removed from the multiplier, and 
another substituted for it, in which strong solution of potassa 
occupied the place of the nitric acid, being in contact with 
platinum in one cup, and solution of nitre in the other, with 
the same communications. The deviation was now much 
weaker, about 10 degrees, and the platinum in the solution 
of potassa was positive. 
The nitric acid and the solution of potassa were now con- 
nected in the arrangement by a piece of clean asbestus, mois- 
tened in a concentrated solution of nitre ; the deviation of the 
needle was to about 65°. In this instance there was no che- 
mical action of the fluids on each other ; for they had no 
tendency to mix rapidly with the solution of nitre, which 
being of less specific gravity than either of the other solu- 
tions, remained in the asbestus ; and there was no effect 
beyond that of the metallic contact of the platinum with acid 
and alkali. 
A piece of asbestus, of nearly the same size with the other, 
