FERTILIZERS. 55 



feet state of preservation. Single teeth are sometimes 

 found as large as a man's hand, weighing over two pounds. 

 These nodules were carted out of fields as waste, just like 

 any other rock, until the querying chemist touched them 

 with his wand. The rocks are ground, and the finer por- 

 tions of them, called " floats," sometimes applied directly 

 to the soil ; and when that is rich in organic matter, or 

 when vegetable matter can be added by ploughing under 

 green crops, it has been found to do quite well without 

 having been treated with acid. Says Professor Dabney of 

 the North-Carolina experimental station, " On sandy soils, 

 or soils destitute of .vegetable matter, it appears to have 

 no effect whatever ; and, when tested by ammonium citrate, 

 but an insignificant portion of the finest ground, called 

 4 floats,' was found to be soluble." Composting in fer- 

 menting manure is recommended, to ascertain whether it 

 cannot be dissolved in sufficient quantity to economically 

 improve the manure. On some of the lands in Scotland 

 it has been used with success as a paying investment with- 

 out having been first treated with acid. 



These mineral phosphates are the great source for 

 phosphoric acid ; for, at the rate commercial fertilizers 

 are now used, bones could not begin to supply the de- 

 mand. The soluble phosphoric acid, whether made from 

 bones, apatite, phosphatic guanos, or the mineral phos- 

 phates of the Carolinas, have been found by careful tests 

 to be all of equal value as plant-food; though the pub- 

 lic, for old acquaintance' sake, naturally prefer that made 

 from bones. Some manufacturers of fertilizers, from hav- 

 ing superior facilities for collecting them, and knowing 

 the prejudice of the public, get the phosphoric acid that 

 they use in their fertilizers wholly from bones. This much 

 may be said in their favor, that, should any of the bone 

 remain undissolved when treated with the acid, it would 



