96 THE MEDALS OF CREATION. Cuap. VI. 
large quantity of white earth sent from New Zealand as 
native magnesia, he found to consist wholly of frustules 
of diatomaceze, chiefly of Galionelle. (See Lign. 5.) 
In America, recent beds of this kind of great extent 
have been observed and examined by that distinguished 
microscopist, Dr. Bailey, Professor of Chemistry in the Mili- 
tary Academy at West Point : and the pages of that excel- 
lent scientific periodical, Silliman’s American Journal of 
Science, are enriched with figures and descriptions of the 
microphytes of which they are mainly composed. 
But the Tertiary formations contain strata of this nature, 
which far surpass in the abundance and variety of their 
organic contents, any of the modern deposits we have 
noticed. The Polierschiefer, or polishing-slate of Bilin, is 
stated, by M. Ehrenberg, 
to form a series of strata 
fourteen feet in thickness, 
entirely made up of the 
siliceous shells of Galzo- 
nelle, of such extreme 
minuteness, that a cubic 
ee inch of the stone contains 
forty-one thousand mil- 
lions. The Berghmehl (mountarin-meal, or fossil farina), 
of San Fiora, in Tuscany, is one mass of these organ- 
isms. 
In Lapland a similar earth is met with, which, in times of 
scarcity, is mixed by the inhabitants with the ground bark 
of trees, for food ; some of this earth was found to contain 
twenty different species of alge. 
In the district of Soos, near Egra, in Bohemia, a fine 
white infusorial earth occurs, about three feet beneath the 
surface ; this substance, when dried, appears to the naked 
eye like pure magnesia, but under the microscope is seen 
to be mainly constituted of elegant disciform cases of a 
FossIi GALIONELLE; highly magnified. 
