ARTIFICIAL MANURES 367 



of their action was enormously increased by grinding them to a coarse 

 meal. Rape-dust was not known in the South of England at the 

 beginning of the Victorian era. In 1840 Liebig suggested the treat- 

 ment of bones with sulphuric acid, and in 1843 Lawes began the 

 manufacture of superphosphate of lime, and set up his works at 

 Bow. So far the chemists ; the next step was taken by geologists. 

 At the suggestion of Professor Henslow, the same treatment to 

 which bones were already subjected was applied to coprolites, and 

 the rich deposits of Cambridgeshire and other counties, as well as 

 kindred forms of mineral phosphates, imported from all parts of 

 the world, were similarly " dissolved." Even Peruvian guano was 

 subjected to the same treatment. Another important addition to 

 the wealth of fertilising agencies was made by Odams, who about 

 1850 discovered the manurial value of the blood and garbage of 

 London slaughter-houses, mixed with bones and sulphuric acid. 



It is in the means of applying appropriate manures to lands 

 which are differently composed, and to crops which vary in their 

 special requirements, that modern farmers enjoy exceptional 

 advantages over their predecessors. The active competition of 

 rival manufacturers assisted the adoption of the new fertilisers. 

 Many men, who would not listen to the lectures of professors, or 

 read the articles of chemical experts, were worried by persistent 

 agents for the sale of patent manures into giving them a trial. 

 Indirectly, their use led to clean farming. A farmer who had paid 

 10 a ton for manure was unwilling to waste half its value on wet 

 ill-drained land. He was less likely to allow it to fertilise weeds, and 

 the more ready to buy a machine to distribute it carefully. Thus, 

 as consequences of purchased fertilisers, followed the extensive use 

 of the drain-pipe, the drill, the hand-hoe, and the horse-hoe. Yet 

 chemical science did not at once fulfil the sanguine expectations 

 which were formed of its capacity in the early " Fifties." The 

 confident hope that the specific fertility extracted by a crop could 

 be restored by a corresponding manure was scarcely confirmed by 

 experience ; and many a farmer did himself as much harm as good 

 by the application of fertilisers which were unsuited to his land. 



Manure and drainage acted and reacted upon one another : the one 

 encouraged the other. Previous rules of successive cropping were 

 revolutionised ; more varied courses were gradually and universally 

 introduced. The old exhausting system of two or three crops 

 and a bare fallow was abandoned when land had been drained, and 



