OF AGRICULTURE. 9 



within the soil, and the small amount of ammonia 

 which he demonstrated to exist in the atmosphere. 



Upon the whole, De Saussure concluded that air 

 and water contributed a much larger proportion of 

 the dry substance of plants than did the soils in 

 which they grew. In his view a fertile soil was one 

 which yielded liberally to the plant nitrogenous 

 compounds, and the incombustible or mineral con- 

 stituents ; whilst the carbon, hydrogen, and oxygen, 

 of which the greater proportion of the dry substance 

 of the plant was made up, were at least mainly 

 derived from the air and water. 



From what has been stated, it will be seen that 

 anything like a consistent scientific explanation of 

 vegetable and animal production was impossible 

 until comparatively very recent times. In fact it is 

 clear that agricultural chemistry properly so called 

 is not a century old ; whilst, without a knowledge of 

 it, the scientific principles of agriculture could not be 

 taught. 



What then is agricultural chemistry 1 It is the 

 chemistry of the soil, the chemistry of the atmo- 

 sphere, the chemistry of vegetation, and the chemistry 

 of animal life and growth, in their bearings on 

 agricultural production. 



Obviously vegetable and animal physiology are 

 essential elements in the explanation of many of the 

 phenomena of agricultural production ; but for any- 

 thing more than necessary passing reference to these 

 branches of science you must look to the distin- 

 guished Professors of Physiology and Botany now 

 attached to this University. 



To Sir Humphrey Davy we owe the first sys- 

 tematic attempt to apply scientific principles to the 

 elucidation and improvement of agricultural practice. 



