1918] CURRENT LITERATURE 287 
Economic importance of diatoms.—MAnw’ gives an interesting discussion 
of the uses of diatoms. Among these he enumerates the use of fossil diatoms 
as abrasives in polishing powders, tooth powders, etc. They have also been 
used as a food adulterant by mixing with flour, thus increasing the bulk of food 
but adding nothing to its nutritive value. They were used in this way by the 
“Earth Eaters.” A later similar use was as an adulterant of candy, but this 
use is now prohibited by law. They were also formerly used as an absorbent 
of nitro-glycerine in the manufacture of dynamite. There are beds of diatomite 
several hundred feet thick on the Pacific coast, and the use of them as a sub- 
stitute for asbestos in packing steam pipes, as filler for refrigerators, and in the 
manufacture of pottery is increasing. Another new use in medicine is as a 
filter forserums. It is suggested that their beautiful designs be used as patterns 
in the ornamentation of jewelry, wall paper, etc. 
ince diatoms store their food in the form of oil instead of starch, it is 
believed that they have been one of the sources of petroleum. On account of 
their being so minute that living ones may be carried great distances in the 
ocean, they may be of use in determining the direction of ocean currents. One 
argument that supports NANSEN’s theory that there is a current passing north- 
ward from Behring Strait across the north polar regions and down the coast 
of Greenland and Norway is that the diatoms of these localities are of similar 
species. Perhaps the one use that is of supreme importance is the furnishing of 
food either directly or indirectly for aquatic animals. Diatoms are chlorophyll- 
bearing plants, and are the greatest agency in the water for changing inorganic 
into organic matter, hence a knowledge of diatoms is fundamental to a study 
of the food supply of fish and other aquatic animals. Animal life is very 
abundant on the shores of the Antarctic continent, and in that region there is 
very little land vegetation. The greater part of the food for all of these animals 
is supplied originally by the diatoms. 
The statement that EHRENBERG estimated the number of individuals in a 
cubic inch of diatomite at 40,000,000 should be 40,000,000,000. The statement 
is made that diatoms are so minute that roo of them could be placed on the 
head of a pin. This is well within the facts, for that number of the smallest 
could find room on the point of a pin. The use mentioned of the diatoms 
Pleurosigma angulatum and Amphipleura pellucida as test objects for micro- 
scope objectives has been discontinued. The Bausch and Lomb Company 
State that the ‘Abbe test saga is now used entirely and is more ecrarate 
and reliable.—C. J. Erm 
Addisonia.—The second number of the second volume of this finely 
illustrated series, issued June 30, contains colored plates and popular descrip- 
tions of Solidago juncea, Echeveria multicaulis, Catasetum viridiflavum, Sagittaria 
latifolia, Baccharis halimifolia, Xanth texanum, Secum Bourgaei, Cimicifuga 
Simplex, Feijoa Sellowianus. and Aster amethystinus. 
® MANN, ALBERT, a economic importance of the diatoms. Smiths. Rep. 1916: 
377-386. fag I~. 
