The Progress of Scientific Agriculture. 429 



of tliaL from those exposed to the full brunt of atmospheric 

 influences ; and when he saw the teamer's eyes watering from 

 the pungent exhalations of the dung-carts, lie maintained that, 

 by the action of the solar rays and the absorptive powers of 

 the breeze, the farmer was being robbed of many of the valu- 

 able fertilizing constituents of his farmyard.^ 



By such discoveries as these the way was paved for those 

 eight epoch-making lectures of Sir Humphrey Davy, delivered 

 before the Board of Agriculture in 1812. Of these, the first 

 was a general introduction to the subject ; the second, a sketch 

 of the principles of physical science especially as affecting 

 vegetables ; the third, a description of the structure and 

 chemical constituents of plants ; the fourth, related to the 

 analysis of soils ; the fifth, to the atmosphere and functions of 

 vegetation ; the two next to vegetable and mineral manures ; 

 and the last to the effects of burning and irrigation, and to 

 the economy of crops. An appendix contained the results of 

 an elaborate series of experiments on the nutritive matter 

 afforded by grasses, performed at Woburn by order of the 

 Duke of Bedford. 2 



The services that Davy thus rendered to agriculture can 

 be best realised by a short study of those theories which 

 influenced farmers before his lectures came into their posses- 

 sion. The fact that plants wither when deprived of water 

 induced many chemists to attribute to this liquid the sole 

 means of nourishment required for vegetable life. Some 

 credited oil with this virtue, others air, others some special 

 salt, while Tull and his school, as we have seen, believed that 

 the earth's upper crust contained an inexhaustible fund of 

 vegetating food, if onl}^ it was reduced to a form palatable for 

 plant life. The root fibres were so many tiny mouths which 

 were unable to masticate their proper food unless it was 

 pulverised into minute morsels. To Tull therefore the only 

 fertilisers were farming implements specially adapted to this 

 purpose. Many of these ideas contained half truths, which 

 Davy now utilised in his laboratory. No two chemists had 3'et 



' Annala of Ayriculture,^ vol. i. p. IG'J, 1784. 



^ Quarterly lieview : "Davy's Agri. Chemistry." July, ISl-A. 



