856 Transactions of the American Institute. 



fractured and -worn by rolling under tlie waves of seas that once 

 swelled where the dry land now lies. Phosphoric acid exists in . 

 abundance in these deposits, but in various degrees of solubility ; for 

 we find that those in the so-called crag formation are very hard, so 

 that they must .J>e crushed by strong machineiy made especially for 

 the purpose, and then treated with sulphuric acid before they are fit 

 for use. On the other hand, the fossils which are found, but in less 

 abundance, in the green sand, may be made sufficiently fine by com- 

 mon machinery, and need no chemical treatment to render the phos- 

 phates soluble in the soil. As a special manure these last named 

 fossils are said to be particularly adapted to the culture of hops ; and 

 one parish in England is noted for its excellent growth of this crop, 

 which is ascribed to the presence of this kind of organic remains in 

 the soil ; and a fair inference from this would be, that any preparation 

 of phosphate of lime would be found advantageous in the culture of 

 the hops, which it may be mentioned is now treated principally with 

 barn-yard manure, and in some cases with lime, the use of the latter 

 except in- alluvial or upon very moist, clay soil, in many cases doing 

 much more harm than good. The fossil phosphates, although capable, as 

 just explained, of very efficient application, constitute only a small por- 

 tion of the phosphates employed in agi'iculture, and may, upon the 

 whole, be considered inferior in value to that existing in the common 

 form of bones. It is now upwards of half a century since bones, 

 broken into pieces with hammers, were first applied as manure 

 in the west of England, great quantities in this form being 

 required for a comparatively small area, but showing benefi- 

 cial results many years after their application ; but it was soon 

 found more advantageous to grind them to a coarse powder in mills, 

 for in this case a smaller quantity would, as far as immediate results 

 are concerned, yield as good results, the usual plan being to apply 

 from sixteen to twenty bushels per acre for turnips, for which the 

 use of bones has been found beneficial in the extreme. This method 

 of powdering the, bones continued in universal use until Liebig's dis- 

 covery of superphosphate, which, as being the most approved vehicle 

 for supplying phosphoric acid to the soil, merits an extended expla- 

 nation of its composition, manufacture and uses. We have already 

 seen that the phosphoric acid from the plants «aten by the animals is 

 for the most part stored up in the bones of the latter, where, in com- 

 bination with lime, it forms the principal part of their inorganic or 

 earthy portion. The ])liosphoric acid and lime together consti- 



