76 DIATOMS. 



in comparative abundance which are very rare elsewhere. 



Back of Sing Sing some three miles, on the site of an 

 old pond long since dried up, is a fresh water deposit of 

 pure diatoms unmixed with any foreign matter worth 

 mentioning. Prom similar fresh water deposits the 

 polishing powder known as electro-silicon and the Star 

 Polishing Powder are made and the Sozodont tooth 

 powder (not the liquid Sozodont, which is a soapy fluid) 

 is made, from a deposit at or near Troy, New Hampshire. 

 This latter is mixed with arrow-root, starch and various 

 flavoring substances. 



That exceedingly energetic explosive, dynamite, is 

 made by mixing nitro-glycerine with a diatomaceous 

 earth from Germany. 



Other sources from which we obtain a supply of dia- 

 toms are somewhat curious. Some of the most beauti- 

 ful of known species are found in the guano from Peru 

 and Southern California. They get there in a roundabout 

 way. 



The diatoms are eaten by minute sea-animals, crusta- 

 ceans, etc. These in their turn are eaten by fishes, and 

 the latter fall a prey to the sea-gulls. As the shells of 

 the diatoms are utterly indigestible, even the rugged 

 gizzard of a sea-gull can do nothing with them and they 

 are deposited intact on the rocks. The stomachs of 

 fishes, oysters, sea- slugs and other marine creatures some- 

 times furnish many rare and curious species. Sound- 

 ings from the deep sea have brought up many kinds 

 hitherto unknown, and washings from the anchor chains 

 of ships have yielded their quota of diatoms. 



The number of species and varieties is enormous. A 

 catalogue was written in 1885 by a man named Habir- 

 shaw. This gave the names of all the species then 

 known and references to all the information regarding 

 them which had been published. This catalogue was 

 never printed, but about fifty copies were made bjj an 



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