Infusorial Earth and its Uses. 
338 
fjuly, 
famous for its occurrence, there is a single stratum of this 
material, not less in some places than 18 feet in thick- 
ness, and extending over a large area. This stone, when 
seen beneath the microscope, is found to consist of the 
siliceous plates or frustules of the above-mentioned diato- 
macese, united together without visible cement, and so 
inconceivably minute are the particles of which it is com- 
posed that, according to Ehrenberg’s statement, a single 
cubic inch, which weighs about 220 grains, contains about 
41.000. 000.000 of individuals, and a single grain no less than 
187.000. 000. Other deposits of infusorial earth (kieselguhr), 
scarcely less extensive, occur in Germany, at Berlin, and at 
Planitz, in Saxony. It is found near Liineburg, in a stratum 
nearly 28 feet in thickness, and again at Kliecken, near 
Dessau, and in the vicinity of Cassel. In England, deposits 
of considerable magnitude have been found in Surrey, at 
the base of the chalk hills, and elsewhere. In Ireland there 
is a celebrated stratum on the banks of the River Bann, in 
the county of Down, and which, from being in much request 
for polishing plate, is locally known as Lord Roden’s plate 
powder ; another bed is found at the base of the Mourne 
Mountains in the same county. In Lapland a similar earth 
is met with, which in times of scarcity, it is said, is mixed 
by the inhabitants with the ground bark of trees and used 
for food. The edible earth of Lillhaggsjon, in Sweden, is of 
the same nature. The infusorial earth is found in quantity 
in the Isle of France and at San Fiora, in Tuscany, and 
deposits of various thicknesses have been detected in Africa 
(the tripoli of commerce is an infusorial earth that has long 
been exported from the country whose name it bears), Asia, 
Australia, and New Zealand. In America it has been found 
in a great number of localities, and occasionally in enormous 
quantities. Of this nature are the beds of white earth 
along the banks of the Amazon, in Brazil, and used 
occasionally as food (?) by the native inhabitants. They 
have been detected also in Newfoundland and Labrador. In 
the United States perhaps the most remarkable deposit is 
that upon which the City of Richmond, Va., is built; this 
deposit is, in places, over 20 feet in thickness, and has been 
traced by Prof. W. B. Rogers, who was the first to point 
out its nature, from Herring’s Bay on the Chesapeake, Md., 
to Petersburg, Va., and beyond. At Petersburg the stratum 
is 30 feet in thickness. Beds of the same character and of 
some magnitude have likewise been found in California, 
Oregon, and other points on the Pacific, and at West Point, 
N.Y. ; while of less importance are the infusorial beds at 
