42 DIATOM ACT. r. 



the end. Silex, or sand, of course, is not to be regarded in 

 this connection, as it is as insoluble as the Diatoms themselves. 



Suppose we take a clay or earth, that of Nottingham^ for ex- 

 ample. Cretaceous matter forms but a small part of its sub- 

 stance, which consists, in fact, of Diatomaceous skeletons, more 

 or less adherent through the agency of a mortar, probably a 

 silicate of lime, and of fine siliceous particles, or even sand, 

 less closely connected. To disintegrate a mass, let it first be 

 slaked, as it were, by pouring over it a strong solution of car- 

 bonate of soda, and when, after a time, the whole falls to pieces 

 in lamina} and in dust, let it be boiled for fifteen or twenty 

 minutes in a quantity of the same solution, and the result will 

 be the reduction of the cement, the formation of silicate of 

 soda and carbonate of lime, and the almost perfect cleaning of 

 the Diatoms. The former is removable by hot water and fre- 

 quent washings; the latter, by boiling in nitric acid; while 

 chlorhydric acid dissolves out any sulphate of lime, and, be- 

 sides, bleaches by the abstraction of unattacked metallic stains. 

 The fine siliceous dust, the torment of diatomists, can only be 

 gotten rid of by elutriation, as will presently be shown, and re- 

 fractory particles or lumps must be left behind in the washings. 



If the reader have followed owe proces raisonne, he will hardly 

 be at a loss to answer the query, " What are we to do with such 

 clay or rock as the Monterey?" some specimens of which we 

 have found to be extremely hard or tenacious. In this in- 

 stance, again, the difficulty presented is the disintegration of 

 the rock without doing injury to the Diatoms. We may make 

 the mass very hot and then drop it into cold water, by which 

 many Diatoms will be sacrificed; or else we may slightly warm 

 the specimen, drop it into a strong solution of carbonate of pot- 

 ash, and boil for a time, to be ascertained by the breaking down 

 of the original lump. In the same way, carbonate of soda 

 may be employed, with more safety to the forms in request, 

 but with less general success; while the potash, which is more 

 energetic in decomposing the cement, is very destructive, if 

 not carefully watched, of the very objects we seek. 



Once reduced to the state of powder, the rules just enunci- 

 ated are to be followed. 



Before leaving the difficult or troublesome, we feel obliged to 



