INFUSORIA AND OTHEE ANIMALCULE. 249 



of themselves an aliment of sufficient nutriment to 

 sustain life ; but in China, where " mountain meal " 

 abounds in some districts, the poorer classes can, 

 by its means, subsist twice as long upon the same 

 supply of provisions as they could do were they not 

 to make use of it. 



This farinaceous substance consists principally 

 of the remains of infusoria and microscopic vege- 

 tables. Under the microscope we recognize in it 

 Navicula viridis, Gallionella sulcata, Gomphonema 

 gemmatum, and several other species. 



Berzelius and Retzius affirm that, at the ex- 

 tremity of Sweden, the peasants are in the habit of 

 eating this infusorial earth to such an extent, that 

 every year many hundred cart-loads are extracted 

 by them from the strata in which it is found. 

 Some eat it from habit or taste, as we smoke 

 tobacco ; others from pure necessity.* Certain de- 

 posits of this kind serve for other purposes, as we 

 shall see presently. 



In America, deposits of infusorial earth have 

 been discovered at West Point; then at Connec- 

 ticut, Rhode Island, Massachusetts, and Maine, in 

 which provinces no less than thirteen localities 

 have been found where this " mountain meal " exists. 

 Some of them have as much as fifteen feet in 



* Compare with this Humboldt's " Views of Nature," 

 the earth eaten by the Otomacs, etc. 



