182 
glass connected with the negative side of the battery. 
" These facts, therefore," to repeat the language of 
Mr Davy, " seem fully to invalidate the conjectures 
of M. Ritter and some other philosophers, with re- 
gard to the elementary nature of water, and perfect- 
ly to confirm the great discovery of Mr Cavendish." 
449. Such, then, is the general mode in which 
Galvanic electricity exerts its chemical action ; but 
let us farther observe, separately and more minute- 
ly, what happens at each pole of the battery. First, 
then, at the positive pole, a particle of water, for ex- 
ample, is decomposed ; its oxygen is attracted, and 
its hydrogen is repelled. But this is not all that hap- 
pens ; for the attracted oxygen combines, in most in- 
stances, with the metallic wire, and thus we observe 
not only the act of decomposition, but that of combi- 
tion also. 
450. At the negative pole, the operations are some- 
what different. A particle of water is here, also, de- 
composed ; but its hydrogen is attracted, and its oxy- 
gen is repelled. The attracted hydrogen, however, 
does not combine, like the oxygen at the opposite 
pole, but passes off in a gaseous form. Hence the 
electricity, accumulated at the negative pole, is 
sufficient only to separate the elements of the com- 
pound, but not to combine them anew; and it may, 
therefore, be said to accomplish decomposition only, 
while the other pole effects combination also. So 
truly is this the case, that silver, says Mr Davy, 
though one of the least oxidable of the metals, easily 
unites with oxygen when it is positively electrified, 
while zinc, one of the most oxidable, is incapable of 
