OF AGRICULTURE. 15 



had been determined ; next by the labours of De 

 Saussure, to which we owe a near approach to a quan- 

 titative representation of the phenomena of vege- 

 tation, which had thus far only been qualitatively 

 observed. To De Saussure we also owe a clear per- 

 ception of the importance, and of the sources, of both 

 the nitrogen, and the ash-constituents, of plants. Then 

 followed Davy, with the first attempt to give a sys- 

 tematic view of the relations of practice with science 

 in agriculture ; Thaer, who traced the fertility of 

 soils to the residue of previous vegetation which they 

 contained ; Sprengel, who contributed much experi- 

 mental result on various branches of the subject ; and 

 lastly Boussingault, who had not only still further 

 extended experimental enquiry, but brought both 

 his own and previous results to bear upon the eluci- 

 dation of long-recognised agricultural practices. 



There can be no doubt that the data supplied by 

 the researches which have been referred to, and espe- 

 cially those of De Saussure, Davy, Thaer, Sprengel, 

 and Boussingault, contributed important elements to 

 the basis of established facts upon which Liebig 

 founded his brilliant generalisations. Indeed, so ob- 

 vious was this, that, in 1841, Dumas and Boussingault 

 published, jointly, an essay which afterwards appeared 

 in English under the title of ' The Chemical and 

 Physiological Balance of Organic Nature,' which was, 

 in fact, a sort of ' reclamation/ 



Nor can there be any doubt that the appearance 

 of Liebig's two works, ' Organic Chemistry in its 

 applications to Agriculture and Physiology' in 1840, 

 and * Animal Chemistry, or Organic Chemistry in its 

 applications to Physiology and Pathology' in 1842, 

 constituted a very marked epoch in the history of 

 the progress of Agricultural Chemistry. In the 



