14 HISTORICAL INTRODUCTION. 



wrote, how feeble was the light that chemistry could 

 throw upon the fundamental questions of agricultural 

 science ! The chemical nature of the atmosphere was 

 then a discovery of barely twenty years' standing. 

 The composition of water had been known but twelve 

 years. The only account of the composition of plants 

 that Earl Dundonald could give was the following: 

 ' Vegetables consist of mucilaginous matter, resinous 

 matter, matter analogous to that of animals, and some 

 proportion of oil. . . . Besides these, vegetables con- 

 tain earthy matters, formerly held in solution in the 

 newly-taken-in juices of the growing vegetables.' To 

 be sure, he explains by mentioning in subsequent 

 pages that starch belongs to the mucilaginous matter, 

 and that on analysis by fire vegetables yield soluble 

 alkaline salts and insoluble phosphate of lime. But 

 these salts, he held, were formed in the process of 

 burning, their lime excepted; and the fact of their 

 being taken from the soil and constituting the indis- 

 pensable food of plants, his lordship was unacquainted 

 with. The gist of agricultural chemistry with him 

 was, that plants ' are composed of gases with a small 

 proportion of calcareous matter ; for although this dis- 

 covery may appear to be of small moment to the prac- 

 tical farmer, yet it is well deserving of his attention 

 and notice.' " 



De Saussure. 



The year 1804 witnessed the publication of by far 

 the most important contribution made to the science 



