M.—AGRICULTURE., 235 
investigations into causes did not directly influence agriculture, but they 
provided the basis on which further development soon came. In 1837 
Liebig had attended the Liverpool meeting of the Association, and he 
urged upon British men of science to study organic chemistry, ‘ which, 
when taken in conjunction with the researches of physiology, both animal 
and vegetable, which have been so successfully prosecuted in this country, 
may be expected to afford us the most important and novel conclusions 
respecting the functions of organisation.’ The very shrewd promoters of 
the meeting replied by asking him to prepare a report on the state of 
Organic Chemistry and Organic Analyses. This never came ; instead, in 
1840, he published a volume, ‘ Chemistry in its Application to Agriculture 
and Physiology,’ stating in the introduction that it was a report presented 
to the British Association, though it is not mentioned in the proceedings 
of any of the meetings. Without exaggeration this can be described as 
the most important publication in the whole history of agricultural 
science. It brought together the results of the plant physiologists and 
deduced from them the principles underlying the nutrition of plants, 
emphasising the fundamental importance of the ash constituents, phos- 
phates and potassium, magnesium and calcium compounds, which 
no one had previously noticed. Prior to that farmers had been told to 
supply humus as the source of carbon. Liebig pointed out that carbon 
was one of the things farmers need not supply, as it was present in 
unlimited quantities in the air; nitrogen also, like carbon, came from 
the air, and need not be supplied. On the other hand, the ash constituents 
came from the soil, and might easily be lacking ; these, therefore, must be 
supplied. The proper way of manuring was to provide ash constituents, 
not organic matter. The new ideas were exceedingly simple; agriculture 
suddenly became a branch of chemistry backed by the great Liebig himself. 
The feeding of crops became almost a matter of arithmetic; the ash of 
a crop contains so much of a certain element, therefore so much must be 
present in the soil or added in the manure. Men of science rose to the 
situation. Murchison, President of the Association in 1846, urged agri- 
cultural members to make use of the Association for the solution of their 
problems. ‘ And if, above all, they wish us to solve their doubts respecting 
the qualities of soils, or the effects of various manures upon them, our 
chemists are at hand.’ We are grateful to our distinguished President 
for making no such promise on our behalf at this Meeting. Meanwhile, 
a much younger man was beginning his-work. John Bennet Lawes, the 
owner of Rothamsted, had studied at Oxford from 1832 to 1834, attending 
the lectures of Prof. Daubeny and seeing his continuous plot experiments. 
On his return to Rothamsted he began pot experiments with various 
plants, and soon found that growth was improved by sulphate of ammonia, 
a waste product from gas works. This was not a new discovery, but it 
was not widely known. Further, he tried another waste product, animal 
charcoal (which contains much calcium phosphate), and found that it too 
was effective, especially after treatment with sulphuric acid when the 
soluble phosphate, then called superphosphate of lime, was produced. A 
neighbouring landowner put to him the Agricultural Society’s problem : 
Why are bones effective on some soils and not onothers? He showed that 
treatment with sulphuric acid was all that was necessary to make them 
