580 
PROFESSOR JOHNSTON’S LECTURE. 
pared with what was thus discharged into the atmosphere. If this 
were so, they could see how it was that plants required a great 
deal more of this nitrogen in their food than had hitherto been 
supposed, and that the combinations it must form in plants were 
more numerous than had hitherto been ascribed to it. He should 
not be going too far in saying that a thousand pounds would be 
well spent if it could be made to clear up this important subject of 
inquiry. 
He would now touch on another point. They had all heard of 
the infusorial animalculse which the oxy-hydrogen microscope 
shewed to swarm in a drop of stagnant water, and which abounded 
wherever water and decaying vegetable matter existed together. 
They abounded in most soils ; did they not abound in all ? If not 
in all, in what soil were they most abundant'! Did they, like 
larger insects, prey on living plants ? Had they any thing to do 
with the ravages committed on clover and corn ? Another import- 
ant point, too, was the various processes by which bogs might -be 
reclaimed. 
Here, then, was a field of inquiry rich in promise, and the culti- 
vation of which demanded the united labour of the out-door expe- 
rimentalist, the chemist, the microscopist, and the geologist. He 
might also draw their attention to other important inquiries, such 
as the influence of light on vegetation, the feeding of stock, dairy 
husbandry, and the best mode of promoting the growth of wool, all 
of which it was desirable to enter upon with the united aid of the 
practical and scientific agriculturist. But who was to undertake 
the inquiries he had named? Some thought that they lay within 
the provinces of an agricultural college ; but the proper province of 
a college was to teach, not to investigate ; to diffuse existing know- 
ledge in the first place, and in the second place to enlarge that 
knowledge. Others thought that our agricultural associations should 
embrace these objects. 
No doubt these means existed, and such bodies might very fitly 
undertake these objects, but he would not venture to enter into the 
question as to how this end might be best effected ; his purpose 
was rather to suggest materials for future thought and consideration 
than to lead them to the adoption of any plan of his own. He 
could not help feeling a kind of regret in thus indicating to others 
trains of research so interesting to follow to himself, in thus, as it 
were, discovering to a stranger the secret of hidden treasure he had 
hoped himself to dig up. In this progress of knowledge, in thus 
helping forward in some new track, there was so great a charm and 
an honour, that were it possible, with the means and life of one 
person, he should himself attempt to carry forward wh'at he had 
suggested, and he should scarcely have ventured to point out to 
