corrosion of copper sheeting by sea zvater, &c. 153 
are now generally adopted, it is evident that soda and mag- 
nesia cannot appear in sea water by the action of a metal, 
unless in consequence of an absorption or transfer of oxygene. 
It was therefore necessary for these changes, either that 
water should be decomposed, or oxygene absorbed from the 
atmosphere. I found that no hydrogene was disengaged, 
and consequently no water decomposed : necessarily, the 
oxygene of the air must have been the agent concerned, 
which was made evident by many experiments. 
Copper in sea water deprived of air by boiling or exhaus- 
tion, and exposed in an exhausted receiver or an atmo- 
sphere of hydrogene gas, underwent no change ; and an ab- 
sorption in atmospherical air was shown when copper and 
sea water were exposed to its agency in close vessels. 
4. In the Bakerian Lecture for 1806, I have advanced the 
hypothesis, that chemical and electrical changes may be 
identical, or dependent upon the same property of matter : 
and I have farther explained and illustrated this hypothesis 
in an elementary work on chemistry, published in 1 8 1 2. Upon 
this view, which has been adopted by M. Berzelius and some 
other philosophers, I have shown that chemical attractions 
may be exalted, modified, or destroyed, by changes in the 
electrical states of bodies ; that substances will only combine 
when they are in different electrical states ; and that, by 
bringing a body naturally positive artificially into a negative 
state, its usual powers of combination are altogether de- 
stroyed ; and it was by an application of this principle that, 
in 1807, I separated the bases of the alkalies from the oxy- 
gene with which they are combined, and preserved them for 
MDCCCXXIV. X 
