20 HOW CROPS GROW. 
was published at London in 1795. It was entitled: “A 
Treatise showing the Intimate Connection that subsists 
between Agriculture and Chemistry.” The learned Earl 
in his Introduction remarked that “the slow progress 
which agriculture has hitherto made as a science is to be 
ascribed to a want of education on the part of the culti- 
vators of the soil, and the want of knowledge in such au 
thors as have written on agriculture, of the intimate con- 
nection that subsists between the science and that of 
chemistry. Indeed, there is no operation or process, not 
merely mechanical, that does not depend on chemistry, 
which is defined to be a knowledge of the properties of 
bodies, and of the effects resulting from their different 
combinations.” Earl Dundonald could not fail to see that 
chemistry was ere long to open a splendid future for the 
ancient art that always had been and always is to be the 
prime support of the nations. But when he wrote, no 
Jonger than seventy-two years ago, how feeble was the 
light that chemistry could throw upon the fundamental 
questions of agricultural science! The chemical nature of 
atmospheric air was then a discovery of barely 20 years’ 
standing. The composition of water had been known but 
12 years. The only account of the composition of plants 
that Earl Dundonald could give, was the following: 
“Vegetables consist of mucilaginous matter, resinous 
niatter, matter analogous to that of animals, and some pro- 
portion of oil. * * Besides these, vegetables contain 
earthy matters, formerly held in solution in the newly 
taken-in juices of the growing vegetable.” 'To be sure ha 
explains by mentioning on subsequent pages that starch 
belongs to the mucilaginous matters, and that, on analysis 
by fire, vegetables yield soluble alkaline salts and insola- 
ble phosphate of lime. But these salts, he held, were 
formed in the process of burning, their lime excepted, and 
the fact of their teing taken from the soil and constituting 
the indispensable food of plaats, his Lordship was unae 
