20 
Mr. Davy's Lecture on some 
acid ; I decomposed the mixture by carbonate of ammonia, 
and I collected and evaporated the fluid part, and decom- 
posed the nitrate of ammonia by heat. About f of a grain 
of fixed saline matter remained, which had soda for its 
base. 
It was possible that the Carrara marble might have been 
recently exposed to sea-water ; I therefore tried, in the same 
way, a piece of granular marble, which I had myself broken 
from a rock on one of the highest of the primitive mountains 
of Donegal. It afforded fixed alkali by the agency of negative 
electricity. 
A piece of argillaceous schist from Cornwall, treated in 
the same manner, gave the same result ; and serpentine from 
the Lizard, and grauwacke from North Wales, both -afforded 
soda. It is probable that there are few stones that do not 
contain some minute portions of saline matter, which in many 
cases may be mechanically diffused through their substance : 
and it is not difficult to conceive the possibility of this, when 
we consider that all our common rocks and strata bear evident 
marks of having been anciently covered by the sea. 
I was now able to determine distinctly, that the soda pro- 
cured in glass tubes came principally from the glass, as I had 
always supposed. 
I used the two cones of gold with the purified water and 
the amianthus ; the process was conducted as usual. After 
a quarter of an hour, the negatively electrified tube did not 
change the colour of turmeric. I introduced into the top of 
it a bit of glass ; in a few minutes the fluid at the surface 
rendered the tint of the paper of a deep bright brown. 
I had never made any experiments, in which acid matter 
