Abstraction of Nitrogen from the Atmosphere. 98 
also with the salt of cont class; likewise with the salt of the 
secondary class, where it is most abundant; and, finally, at 
one locality in the serine class, in the environs of Paris, 
whence, in part, was derived its commercial n 
From the experiments of Mr. Beudant, #5 is 2 genta that 
no marine animal can live in water saturated with gypsum 
Does not this fact militate against the idea of gypsum being 
an original production, existing in solution, since marine ani- 
mals were abundant, and must have lived in the gypseous 
solution? Does it not, on the contrary, seem highly proba- 
ble, that gypsum was formed from its elements, at various pe- 
riods, and in various localities ? 
The admission of the subsequent formation of gypsum, 
explains many facts belonging to the period of its deposition, 
the annihilation of pyrites, so abundant in the primitive one 
if we did not suppose that this mineral, when disengaged fr 
the materials which gave birth to the succeeding classes, was 
operative in the production of gypsum 
Gypsum is a product daily forming in all places where car- 
bonate of lime is present, and pyrites is undergoing its con- 
version to sulphate of iron. The result of the combined 
tion of these substances upon each other, is sulphate of bivie: 
(gypsum,) oxide of iron, and carbonic acid, uncombined, 
when oxygen has access to the iron. 
Whence did the plants, whose remains have produced our 
coal beds, obtain their carbon? Either we must suppose that 
the atmosphere contained more carbonic acid than it does 
now, or we must derive it from the carbonic acid set free 
from limestone, by sulphate of iron. For, in 
state of our knowledge, this is the ree, and the only 
way, in we can rationally account for the 
eou: 
food of plants. As to the supposition of a greater quantity 
of carbonic acid, at that time, in the atmosphere, it is objec- 
tionable, on the ground that it has no support, but from ex- 
plainiug a known fa 
The red colour of the marl of gypsum, and the red rocks, 
as of sandstone, &c. common to the period of gypsum, tend to 
confirm the view that gypsum is not an original product, but 
the result of the combined action of its elements, existing in 
the primitive class of rocks, and in the atmosphere, for the ox- 
ide_ of iron, their calcining matter, is a resultant, as ‘beter 
mentioned. 
