geologists have given the name of the neocomian. The fossils brought home by M. Lewy leave no room for doubt on this subject.
Since the publication of the discovery of M. Lewy, MM. Nicaize and Montigny have found in the valley of the Harrach, in the province of Con-stantine (Algeria), a bed of emeralds, appertaining, like that of America, to the cretaceous formation.
BERYL AND AQUAMARINE.
The beryl and the aquamarine have the general composition and constitution of the emerald; but they differ from it in the absence of the oxide of chromium, which is in them replaced by the oxide of iron. The colour remains the same, but it is much feebler and less pure than in true emeralds.
Beryl.—Among lapidaries and dealers in precious stones the beryl and the aquamarine constitute a well-defined group, altogether distinct from the emerald. With them the beryl is the oriental species of this group, and the aquamarine the occidental.
For a long time the beryl was only known in India; afterwards it was met with in Arabia; and still later remarkable fragments of it were found in Russia, at Beresof, and in the environs of Lake Bolchoi.
