SOURCES OF PHOSPHORUS IN THE MINERAL KINGDOM. 301 



phates, and particularly the phosphate of lime, are the chief 

 hard materials of the bones in vertebrated animals, the car- 

 bonate of lime being in very inferior proportion. In the 

 higher animals phosphates are found generally throughout 

 the fluids and soft parts as well as in the skeleton. 



The acknowledged value of the soluble phosphate of lime, 

 and even of bone-dust, as a manure, has turned the attention 

 of chemists of late to the localities in which phosphate of 

 lime exists mineralised in a more concentrated state than in 

 the common rocks of the earth's crust. Many such localities 

 have been determined, and these promise to become most 

 valuable sources of phosphatic manure. A few of these 

 minerals deserve notice : Norwegian apatite, which is im- 

 ported into Britain in shiploads, contains from 77 to nearly 90 

 per cent of tribasic phosphate of lime or bone-earth. Spanish 

 or Estremadura phosphorite, which occurs in immense quan- 

 tities near Truxillo, in Estremadura, contains nearly 80 per cent 

 of bone-earth. It does not appear to have been yet profitably 

 used as a manure. Bavarian phosphorite, found at Amberg 

 in Bavaria, and containing a small proportion of iodine, is of 

 much the same composition as the Estremadura phosphorite. 

 It has been used in Germany for agricultural purposes, but has 

 hardly yet found its way in quantity to Britain. Osteolith, 

 discovered near Hanau, is very rich in phosphate of lime ; but 

 it cannot be excavated so as to defray the cost. Phosphatic 

 nodules from the lower chalk are known in commerce under 

 the name of Cambridgeshire coprolites. These contain from 

 54 to 58 per cent of bone-earth. Under the name of Suffolk 

 coprolites, pseudo or false coprolites, or crag- coprolites, are 

 known in commerce, the mixed fossil bones, fish -teeth, 

 and phosphatic pebbles, which occur in the tertiary deposit 

 termed Suffolk crag, varying from three to eighteen inches 

 in thickness between the coralline crag and London clay. 



