S26 Dr Wollaston on the Eodstence of Potash in Sea-Water, 
I evaporated a pint of the water which you sent me (mark- 
ed No. 9. specific gravity 10S6.22), taken up by Captain Ross 
in Baffin’s Bay, from the depth of 80 fathoms, latitude 36° 32', 
longitude 76° 46^ west. When this had been reduced to about 
2^0 th part, I drained the hquor from the salt that had form- 
ed, which I also washed with a little water, and, by adding 
muriate of platina to the drained liquors, I had a yellow preci- 
pitate which weighed 12.4 grains. 
“ As the fluid poured from this precipitate measured |th of a 
fluid ounce, I estimate that this would retain in solution about 
three grains of the triple muriate ; and hence the whole amount 
must be taken at 15.4, which, by former experiments, I consider 
as equivalent to about 6.4 sulphate of potash, or 3.5 potash. 
Now, since the pint of water weighed about 7520 grains, 
gives the proportion of potash, about o > quantity of 
mere potash is less than of sea-water, at its average 
density.” 
Dr Wollaston has also detected traces of potash in the water 
of the Lake of Ourmia or Arumea, which is unconnected with 
the ocean. The water of this lake (which is situated in the pro- 
vince of Azerbijan in Persia) is said to be salter than that of 
the sea, so that no fish can live in it. Dr Wollaston is of opi- 
nion, that the potash exists in sea-water in the state of sulphate. 
Art. XXI. — Short Comparison the Volcanic Rocks cf France 
with those q/* a similar natui'e found in Scotland. In a Let- 
ter addressed to Professor Jameson, by Ami Boue', M. D. 
Member of the Wernerian Society^. 
Dear Sir, 
Having lately spent some time in the remarkable volcanic 
districts in the South of France, and knowing the interest you 
have always taken in every thing respecting the geognosy 
• I have much pleasure in laying before our readers the interesting letter of 
my friend and former pupil Dr Boue. During his residence in Scotland, he 
visited and examined many extensive tracts of country, and studied particularly 
