90 HISTORY OF GALVANISM. 



electrical instrument; in other words, whether 

 its primary operation is to produce any chemical 

 change in the metals of which it is composed, or 

 whether it depends merely on the electric action of 

 the bodies upon each other. It has been supposed 

 by some that the phenomena of the electric column 

 originate from a small quantity of moisture, which 

 is still adherent to the paper interposed between 

 the metallic plates ; and experiments have been 

 adduced to prove, that in proportion as the paper 

 is carefully dried, the electric effects are dimi- 

 nished. These observations have not, however, 

 been confirmed, while there are, on the other hand, 

 some circumstances which seem to favour the 

 contrary supposition. The instrument has been 

 known to remain in action for months or even 

 for years, and yet no visible alteration could be 

 perceived on the surface of the metals ; which 

 could scarcely have been the case had any che- 

 mical action existed between the metal and the 

 moisture in the paper. Another circumstance 

 which seems in favour of its being essentially an 

 electrical, rather than a chemical instrument, is 

 the connexion which there appears to be between 

 its action and the electric state of the atmo- 

 sphere. This connexion was perceived by De Luc 

 soon after he had constructed the apparatus, and 

 he made a number of accurate observations upon 

 the subject. Mr. Forster, by a mechanical con- 

 trivance, has adapted a bell to it, which continues 

 to ring with a regular motion in the ordinary 



