DIATOMACEOUS EARTH, 245 



On account of its porosity and compactness diatomaceous earth is used 

 in water filters and as an absorbent of nitroglycerine in the manufacture 

 of dynamite. It is reduced readily to a fine powder, the hardness of the 

 individual particles and their sharp edges making it an excellent base for 

 polishing compounds. Its low heat conductivity makes it a valuable ingredi- 

 ent in the manufacture of packing for steam boilers and pipes, and in the 

 construction of fire-proof safes. It has been frequently utilized for the 

 latter purpose. It has also been suggested that it might be used in certain 

 branches of potteiy manufacture, which require on the part of the materials 

 both refractoriness and an absence of color when burned. 



In 1905, samples of diatomaceous earth were collected around Eichmond 

 and the Kappahannock Eiver, and tested by Dr. Heinrich Eies. The results 

 of the chemical analyses are given in the table above, and those of the 

 physical tests on page 246. 



