PHOSPHATE ROCK. 109 



dried by the addition of bone flour (if you have it) 

 or with dry muck, dry wood ashes, potash salts, etc. ; 

 it is then a complete fertilizer, although, perhaps, 

 not excessively rich in nitrogen. 



If we were compelled to depend for our supply of 



phosphoric acid on the bones of animals of our own 



period, we would be in a bad flx indeed. But it so 



happens that vast quantities of fossil bones— the 



bones of all sorts of animals that inhab- 



^^»ock**^ ited the sea, and swamps, and ponds, etc., 

 probably long before the era of man— are 

 stored up in various parts of the world, especially 

 in North and South Carolina, in Florida and else- 

 where. An immense accumulation of the best 

 article of this kind is found in South Carolina, and 

 this contains from forty to sixty per cent of phos- 

 phate of lime. It is known under the name '' phos- 

 phate rock, or South Carolina rock." 



In order to flt it for use, this rock is ground to a 

 fine powder, and is then called ground South Caro- 

 lina rock, or floats. In this we have about twenty- 

 seven or twenty-eight, sometimes even more, per 

 cent of phosjioric acid, which of course, is wholly 

 insoluble, or very nearly so. The stations rate this 

 form of phosphoric acid at two cents per pound, 

 making the ton worth eleven or twelve dollars. 



If applied in this form to some soils, especially 

 to those destitute of carbonaceous matter (humus), 

 and insufficiently supplied with potash, such as 

 thin, sandy soils, this plain phosphate has usually 

 little or no immediate effect. In soils having potash 

 and carbonaceous matter in suflacient quantity, how- 

 ever, the phosphate flour is very slowly dissolved, 

 and thus made available for plant nutrition. 



Where we desire immediate action of the phos- 



