[307] SCIENTIFIC MANUAL. 21 



bright metallic lustre. It takes fire when exposed to the 

 air, burns with a bright flame and white fumes, and hence 

 has to be kept in water. It cannot exist in the free state 

 naturally, but is always found as phosphoric acid combined 

 with some other element, forming the phosphate of that 

 element. 



Though phosphorus is extremely poisonous to all animal 

 life, in combination with oxygen, as phosphoric acid, it is 

 necessary to the growth and maturity of both plants and 

 animals, forming an important constituent of the stems, 

 leaves and seeds of plants, a large per cent, of the bones of 

 animals, and is contained also in the other parts of the an- 

 imal system. 



As plants derive their mineral elements (except carbon) 

 entirely from the soil, all fertile soils must necessarily con- 

 tain a fair percentage of this important constituent. 



Very many minerals contain phosphoric acid, and it is 

 from their decomposition that soils naturally derive their 

 supply. 



The composition of bones, the best source of phosphoric 

 acid for agricultural purposes, is as follows: 



Animal matter .-33 per cent. 



Lime phosphate 57 " 



Lime carbonate 8 " 



Magnesium phosphate 1 " 



Other ingredients. 1 " 



100 



The chief sources of the phosphates of commerce are 

 the minerals and rocks which contain them, and bones of 

 animals, both fossil and fresh. The most noted beds of fossil 

 bones and rocks are those near Charleston, S. C, which 

 are now largely worked. The rocks and bones there found 

 are the accumulations of the remains of marine animals 

 which once inhabited the waters of the sea that covered 

 that section ages ago. These beds are very extensive, and 



