3 8 A GRICULTUR&. CH. 



" super-phosphate of lime" is really a mixture, of which 

 the active ingredient mono-calcic phosphate forms 

 sometimes not more than one-fourth of the entire weight. 



71. This discovery of Liebig's led to the establish- 

 ment of an entirely new branch of chemical manufac- 

 ture, for although for a time farmers manufactured 

 their own super-phosphate, by purchasing bones and 

 sulphuric acid, it was soon found that a manufacturer, 

 with convenient machinery, could do the work far 

 more advantageously and economically. The late 

 Mr. Thomas Proctor of Bristol was the first manufac- 

 turer of super-phosphate of lime. He was present at 

 the meeting of the British Association when Liebig 

 announced his great discovery. As soon as it was 

 made known he travelled to Bristol with all speed, 

 and at once commenced the manufacture, promptly 

 sending out Liebig's new manure ready for use. The 

 economy of the new process was soon recognized, 

 and the manufacture of artificial manures advanced 

 with incredible rapidity. 



72. The next advance was the discovery of Mr. 

 J. B. Lawes in 1842, whereby he proved that mineral 

 phosphates of lime were capable of being manu- 

 factured so as to produce the same mono-calcic 

 phosphate, which had previously been manufactured 

 solely from bone. This led to an extensive 

 search for rocks, and other mineral deposits contain- 

 ing the tri-calcic phosphates, and the result has been 

 a considerable decrease in the cost of the materials 

 used in the manufacture, which has resulted in a 

 cheaper supply for the farmer's use. The new 

 description of super-phosphate of lime thus introduced 

 was distinguished as mineral super-phosphate, 

 that is to say, super-phosphate of lime manufactured 

 from mineral phosphates. Subsequent experience has 

 confirmed Mr. Lawes' original opinion, and has 

 resulted in super-phosphate of lime being now very 

 largely made by the ; udicious use of mixtures of 



