PHOSPHATE ROCK 439 



results from their use were recoj]:nize(l and appreriated. the 

 real cause of the stimuiatinp^ effect seems not to have hccn 

 definitely recognized until Dr. Justus von Liehip, of (leissen, 

 Germany, evolved the idea that sulpliuric acid should Ix* added 

 to bone fcrtihzers in order to render soluble the piiosj)li:it(' 

 they contained. It was not until the year 1843 that the Duke 

 of Richmond, after an exhaustive series of experiments upon 

 the soil with both fresh and defrelatinized bonos, came to tho 

 conclusion that their value for fertilizing purposes was due 

 to the large quantity of phosphoric acid contained in thrni. 

 To prove this effect a number of vegetables were planted in 

 burnt sand rich in every element of fertility except ])hosphoric 

 acid; no development of the plant took place until calcium 

 phosphate had been added to the sand, but after this addition 

 the growth became flourishing. 



The calcium phosphate in bones had hitherto been con- 

 sidered as useless owing to its insolubility, and the fertilizing 

 element was considered to be the gelatinous matter. Shortly 

 after 1840 Mr. J. B. Lawes put Dr. von Liebig's ideas into prac- 

 tice, and began to manufacture artificial fertilizers at Deptford 

 (London) England, by mixing sulphuric acid with crushed 

 bones. In the yesir 1845 Professor Henslow reconmiended tliat 

 the Cambridge coprohtes, rich in calcium phosphate, should 

 be used as a substitute for bones in making fertilizers, and, 

 acting on this suggestion, the numerous bone crushing works 

 were quickly converted into chemical fertilizer and super- 

 phosphate factories. The coprolites of Cam})ridge were sup- 

 plemented by the phosphate deposits in SufTolk and Bedford- 

 shire, but it was not until twenty five years later that the 

 phosphate mining industry began to assume a commercial 

 importance. This slow growth is attributed to the supply of 

 guano obtained from Peru, the best beds of which did not be- 

 come exhausted until between 1870 and 1875. The failure of 

 this source of supply immediately led to the substitution of 

 other material for the manufacture of fertilizers. 



In France the phosphate deposits at Grand Pre', in the 

 Adrennes, began to be exploited in 1856, and small (juantities 

 of the rock in a ground state were utilized by direct addition 

 to the soil. In 1865 other deposits were discovered on the 



