14 THE SCIENTIFIC PRINCIPLES 



yielded in the milk and excretions of the cow, and 

 in the excretions of the horse. Here, again, tha 

 exigencies of the investigation he undertook were 

 beyond the reach of the known chemical methods 

 of the time. Indeed, rude as the art of agriculture 

 is generally considered to be, the scientific elucida- 

 tion of its practices requires the most refined and 

 very varied methods of research ; and a characteristic 

 of the work, not only of Boussingault, but of most 

 agricultural investigators, may be said to be, that 

 they have frequently had to devise methods suitable 

 to their purpose, before they could grapple with the 

 problems before them. 



In 1839, chiefly in recognition of his important 

 contributions to agricultural chemistry, Boussingault 

 was elected a member of the Institute of France ; 

 and in 1878, thirty-nine years later, the Council of 

 the Eoyal Society awarded to him the Copley Medal, 

 the highest honour at their disposal, for his numerous 

 and various contributions to science, but especially 

 for those relating to agriculture. 



The foregoing brief historical sketch is sufficient 

 to indicate, though but in broad outline, the range 

 of existing knowledge on the subject of agricultural 

 chemistry prior to the appearance of Liebig's me- 

 morable work, ' Organic Chemistry in its applications 

 to Agriculture and Physiology,' the first edition of 

 which was published in 1840. 



It will be seen that some very important, and indeed 

 fundamental, facts had already been established in 

 regard to vegetation ; first by the numerous investi- 

 gations made about half a century previously, by which 

 the composition of the atmosphere, and of water, and 

 the mutual relations of these and vegetable growth, 



