254 THE CANADIAN NATURALIST. [Sept. 



was made upon a gray, infusible fire-clay, which proved, 

 upon analysis, to possess the following percentage com- 

 position : — 



c;i;«n-« Ar,;A S combined silica 37*99? ^ t,^ 



Sihcic Acid ^ f^.^^ ^^^^^ .^Q.^Q I 08-49 



Alumina (by difi'erence) 26 '79 



Iron Cprotox.) , traces 



Lime , 0-12 



Magnesia ^ traces 



Soda t 1-53 



Potassa 1-52 



Chlorine, Ammonia, and Phosphoric Acid , traces 



Organic matter • 08 



Water (Hygroscopic 1-38) 11-47 



100-00 



One hundred grammes of this clay were washed upon a 

 large filter, until the filtrate was quite free from solid matter, 

 and a solution (containing 10 grm. to 1 litre) of phos}Dliate 

 of soda was then caused to filter slowly through the mass, by 

 a syphon arrangement, in about 24 hours. 



The solution extracted a quantity of humic acid, dissolved 

 out by the action of the alkaline salt, and contained only 

 8*312 grammes of jjJiosjjJiate of soda^ with a little alumina, 

 lime, and sesquioxide of iron. Such a clay being, practi- 

 cally a pure silicate of alumina and water, the large absorp- 

 tion is in a great measure due to a reaction between the 

 hydrated silicate of alumina, or clay, and the phosphate of 

 soda, resulting in the formation of a phosphate of alumina, 

 and the fixing of a portion of soda at the same time by the 

 aluminous silicate. 



This power of clay was first explained by Way and Thom- 

 son ; * though it was remarked by the Dean of Westminster 

 in 1849,f who suggests that it is shown by the concentration 

 of phosphates occurring in certain clayey nodules, termed 

 Septaria, common in the Lias of England. 



It is probable, that the formation of many great phosphatic 

 deposits, of marine origin, including perhaps the Canadian 

 apatites, is most reasonably explicable by referring to these 



* R. Agric. Soc. Jom-n. Eng. (xi. 68-74 xii. 317-380 ; xiii. 123-140.) 

 t Brit. Assoc. Report, 1849. 



