IV.] EARLY HISTORY OF SUPERPHOSPHATE 123 



patent, whereupon he disclaimed the use of bone 

 substances included therein. He also declared that he 

 began his manufacture with bone ash, apatite and 

 phosphorite being unobtainable commercially, though 

 in 1843 he imported several tons of the Spanish 

 phosphorite from Estremadura, and early in 1845 began 

 his enquiries if coprolites could be obtained cheaply 

 from the Eastern counties. Gilbert also gave evidence 

 that the manufacture and use of superphosphate on 

 a large scale prior to the date of the patent were 

 matters of common knowledge at Rothamsted when 

 he came there in 1843. Putting aside the fact that 

 Lawes was the iirst man to make superphosphate a 

 practical possibility, there is thus no doubt that 

 he arrived at the idea of the importance of a soluble 

 phosphatic manure quite independently of Liebig, 

 and had tested the idea on a working scale before 

 taking out his patent. The only other point of 

 interest in this early history of superphosphates is that 

 Sir James Murray of Dublin took out a patent a few 

 weeks before Lawes, in which he suggested as manure 

 phosphoric acid prepared by treating phosphorite with 

 sulphuric acid Murray's object, however, was to 

 generate carbonic acid in the ground, and his patent is 

 for a means of " mechanically fixing and solidifying 

 mineral acids " — sulphuric, muriatic, nitric, and phos- 

 phoric — by mixing them with absorbent matter like 

 bran, sawdust, peat, etc., the phosphoric acid thus 

 coming in incidentally only, and not for its own 

 nutritive value to plants. A few years later, to avoid 

 any question of priority that might arise, Lawes 

 purchased Murray's patent, and amended it by dis- 

 claiming everything but the manufacture of a manure 

 by the treatment of phosphorite with acid. 



The early superphosphate thus manufactured by 



