4 
112 On Plaister-of Paris. 
cultural uses, seems to be founded in mere theory. For 
we find by eaperience, of which theory is only the pupil: 
Lj Ape the gyps succeeds on limed land, quite as 
well as on that not limed ; and some think better. 
2. Although we never analyze chemically, to know 
the balance between the acid and. the calcareous earth in 
our plaister, we find that the gyps, out of the same par- 
cel, does as well on Aimed, as on other land, let whatever 
parts of the substance prevail in its composition. 
3. As to its alleged disagreement with alkalis, we 
do not find this, by any means, founded in fact. I have 
plaistered land previously manured with soap boilers 
ashes, and it has not only done well, but I think has had 
remarkable success. ’Tis true these ashes are mixed 
with lime, and the alkali weakened by lixivation. But 
General Hand has placed the fact beyond a doubt. See 
pages 30, 31. He strewed ten or twelve bushels of 
(wood) ashes to the acre, which is much more than I 
ever strew per acre, for grass. The plaister, he states, 
had more effect, than it had on ground dressed with other 
manure. Why it 1s so, is not of so much consequence, 
as the fact itself. But if the foregoing theory were pur- 
sued, we should find encouragement from the proper- 
ties of alkalis. Chaptal, pages 115, 119, 120, [ Philadel- 
phia edition] “all alkalis contain carbonic acid and are 
considered as carbonates. Hydrogene and nitrogene gas 
may be produced from mineral; and carbonic, from all 
alkalis.’ In other chemical writers it appears, that the 
salt-found in ashes, may be purified, so as to contain 
half its weight of fixed air. Beside that it may be pre- 
sumed that vegetable alkalis furnish the most carbone, 
it appears, that in both mineral and vegetable alkalis, the 
