42 



* 



almost entirely of phosphate of lime and magnesia. The supplies 

 of this material mostly come from the L-i Plata districtsof South 

 America and the Baltic, Mediterranean and Black Sea port*. In 

 this manufacture large amounts of ammonia are lost. These 

 two materials, bone black and bone ash, have the phosphate of 

 lime, in a peculiarly sensitive or assimilative condition, and it 

 would be profligate to use them as raw materials for conversion 

 into superphosphates. It seems as if the passing through the 

 animal economy renders phosphate of lime sensitive to assim- 

 ilation. It is only to be regretted that the available supply of 

 these materials is so very limited. 



Apatite. This is a hard mineral, sometimes crystalized, at 

 others conchoidal. It is generally found in thin seams of crys- 

 talline or volcanic rocks. It varies in color from light green 

 to iron stone red. The principal localities in which it is found 

 is Northern Europe, Canada, New York, and New Jersey. 

 The close structure of this mineral, even when finely powdered, 

 makes it unsuited for direct application to soils, and the com- 

 mercial supply is limited, owing to the inaccessibility of its 

 sources. Its conversion into superphosphate of lime is also 

 attended with many manufacturing difficulties. 

 . Phosphorite. This substance is very much like the preceding. 

 It is fibrous in structure, a light yellow color, and very hard ; 

 generally found in thick beds, surrounded by apatite and 

 quartz. It derives its name from becoming phosphorescent 

 when heated ; and the best qualities come from Spain and 

 Bavaria. 



The supply of this article is also very limited, owing to diffi- 

 culty in mining. 



The German, French, and Prussian phosphorites are also in 

 the market but, as a general rule, the percentage of bone 

 phosphate of lime is too low to make them an economical 

 source ot supply, the percentage of sand especially being so 

 large. 



Coprolites True coprolites are not fossil excrements, but 

 worn and rounded fragments of fossil bones. They are chiefly 

 found in England, France, and Germany, and, to a small extent, 

 in Canada. They contain large amounts of fluoride of calcium, 

 carbonate of lime, oxide of iron, and alumina. They do not 

 make a good superphosphate, and are not as good for this pur- 

 pose as the South Carolina phosphate. Nevertheless, in Eng- 

 land they are extensively employed, on account of their- abun- 

 dance and cheapness. 



.Rossa, or G-uayamas Guano. This is a very superior rock 

 guano, from the Island of Rossa, in the Gulf of California. 



It is peculiar in that it contains a portion of its phosphate of 

 lime in the bi-ealcic, or " reduced," state, and is almost wholly 

 free from foreign constituents. It is in hard lumps, but easily 

 powdered. 



