The Progress of Scicntijic Agriculture. 431 



analyses of sunflowers grown by Du Hamel with and without 

 nitre, and the tables of De Saussure, on which were recorded 

 the composition of plants grown in different solutions of salts, 

 Davy rightly decided that soils and manures play a far more 

 important part in the vegetable economy than the continental 

 philosophers who swore by Braconnot had supposed. It was, 

 indeed, precisely the same phenomenon which puzzled Dr. 

 Fordj'ce over his cage-birds. If, at the time of laying, his 

 canaries were deprived of access to carbonate of lime, their 

 eggs were imperfect. But the problem was a far more difficult 

 one than either Davy or Liebig after him had imagined. If, 

 as in the case of the cage-birds, the supply in proper propor- 

 tions of the constituents found in the ashes of ^^^ or plant 

 had been all that was needed, there would have been nothing 

 left for Lawes and Gilbert to discover. If it could have been 

 proved that nitrogen was not essential to plants, or if essential 

 how assimilable by their contact with earth and air, the vast 

 capital spent since in the purchase of expensive nitrogenous 

 manures might have remained in the farmers' pockets. 



By thus accentuating the importance to vegetable life of 

 soils and manures Davy upset numerous preconceived notions. 

 Those farmers who still based their practice on Tull's and 

 others' theories now reverted to the long neglected middenstead, 

 and trusted to the refuse of the stable and byre to increase 

 the productive powers of their farms. Henceforth the humic 

 theory came into fashion ; that is to say, farmers directed 

 their entire attention to fertilisers which would restore to 

 their seed-bed its reservoir of humic constituents as soon as 

 it became depleted by the exhaustive process of vegetation. 

 Davy had thus presented to them the truth, but not the 

 whole truth. He afforded them an insight into the nutritive 

 qualities of their commonest produce. The results both of his 

 quantitative and qualitative analyses of crops were tabulated 

 and placed at their disposal. Henceforth the}' could discuss 

 scientifically the proportions of starch, sugar, and albumen in 

 every used variety of cereal or root ; of lime, silica, alumina, 

 and organic matter in most kinds of soils ; the beneficial quali- 

 ties" of each known manure, and the mechanical effects of 



