102 
TUKORY OF CAJ.VANISM. 
Excitciiu'iit of wliich he says, towards tlie end of his paper, “ Various sa'in« 
r^dtv fomponuds, tinged wiih the most delicate vegetable colours, 
l)iiciioiiicn;i of have been made the medium of communicaiion between the 
tlic dcctric . 
periments have been made with metallic sohnions : but in 
none of these trials have the smallest trace of chemical effect 
appeared.” 
those theories detailed in Mr. Henry’s paper, founded on the 
hypothesis, that the electromotion in the galvanic pile depends 
on its chemical effects. But there is another circumstance 
mentioned by Mr. Singer, which, at the same time that it cor- 
roborates that proof, exhibits the true nature of this natural 
electric machine, proves also, that the electromotion in it does 
not depend on any internal chemical effect. He says, in the 
conclusion of his paper , — “ The cause of the electric excite- 
ment in the column appears to be permanent. I have some 
that have been now constructed upwards of two years, and | 
their power is no way diminished; in the cases when the 
contrary has happened, I conceive the presence of too much 
moisture, and the consequent oxidation of the zinc surface, 
must have been the deteriorating cause.” 
This is an immediate proof that the presence of a liquid is 
not necessary to the electromotion in the galvanic pile itself; 
since, on the contrary, too much moisture in the electric co- I 
lumn, and the consequent oxidation of the zinc surface, is a | 
cause of diminution. This I have found in the course of my | 
experiments on the galvanic pile ; for the electromotion ceases 
in it, and consequently all the other effects, wdien the surface 
of all the zinc plates is deeply oxidated ; so far from that che- 
mical effect being the cause of the electromotion in ihegahanic 
pile. 
I must mention here, that, in speaking of galvanic pheno- 
mena, I refer th.em to their otigin, the galvanic pile, as invented fl 
by Volta, not to the apparatus which is now much used, the 
galvanic troughs. This apparatus has greatly increased the 
•lectromotion and some of its effects ; but ike phenomena are ' 
foluuiu. extremiiies, and the coniac; preseivtd many days : similar ex- 
There cannot be a more peremptory proof of the error of 1 
too 
! 
