NATURE'S JEWELS. 175 



They stand the wear and tear of the elements 

 for thousands of years. They are found in pumice- 

 stone, and -in the ashes of both active and extinct 

 volcanoes, in meteoric dust, in the stomachs of 

 fishes and birds, in the deepest recesses of the 

 ocean, in the pancake ice of the polar regions, amid 

 the mangrove swamps of the tropics, on the moun- 

 tain tops, and in the valleys beneath. Earth, air, 

 and water every clime and country on the globe- 

 are penetrated by Diatoms, either fossil or living, 

 or both. 



Diatoms in their living state constitute a kind 

 of almost universal food ; from the humblest infu- 

 sorian up to man himself, all partake of them in 

 one form or another ; and even their silicious re- 

 mains, mixed and baked with common earth, are 

 sometimes the food of starving man ; while the 

 Japanese make a delicate and nutritious soup with 

 them in their living condition, along with certain 

 kinds of sea- weed. They also add greatly to the fer- 

 tility of the soil, while at the same time increasing 

 its quantity. It is well known that the best guano is 

 that in which Diatoms are most abundant, and that 

 river deposits rich in diatomaceous remains are very 



