PHOSPHATE OF LIME. 219 



roots of plants but never through their leaves and thus 

 exerts its notable effect. If reference is made to the table 

 in which the composition of the ash of plants is given, it 

 will be seen that red clover, the grasses, white clover, and 

 other leguminous plants; and cabbage, turnips, rape, mus- 

 tard, and other plants of the cabbage or cruciferse tribe; all 

 contain a large amount of sulphur and sulphuric acid in 

 their ash. Thus is most clearly explained the peculiarly 

 favorable results of an application of gypsum 100 Ibs. of 

 which convey to the soil 46* Ibs. of sulphuric acid. 



WOOD ASHES, containing as they do all the inorganic 

 elements of plants in a condition in which these are readily 

 appropriated, necessarily make a most effective manure, and 

 are useful to all crops and upon all kinds of soils that are in 

 a proper condition to bear crops. It is unnecessary to say 

 further than this in regard to them. 



PHOSPHATE OF LIME, exists naturally in the form of an 

 abundant rock and is widely dispersed through the soil. It 

 also exists in vast beds, chiefly in North and South Caro- 

 lina near the coast and along the banks of the tidal rivers 

 in the form of remains of marine animals which have ex- 

 isted in past ages. This substance is used in its raw state 

 finely ground, and is known in commerce as Charleston 

 floats from the locality where it is chiefly dug and manu- 

 factured. In this condition it is slowly soluble and has 

 been found to exert a favorable effect upon such crops as it 

 has been applied to, chiefly those however which are grown 

 for their seed, as cotton; corn; wheat; and other grains. It 

 is of most importance however in regard to its use for the 

 manufacture of super phosphate of lime to be hereafter 

 described. In the form of "floats" it is used at the rate of 

 about 1000 Ibs. per acre. These floats are ground as fine as 

 flour, and although practically insoluble in pure water, are 

 dissolved to some extent by water containing various acids, 

 more especially carbonic acid, which acts upon the lime and 

 so releases the phosphoric acid. This form of phosphate of 

 lime contains from 24 to 49 per cent, of phosphoric acid, 

 and the low price at which it is sold and the favorable me- 



