OF SELBORNE. O57 
and to oblige the young to seek for new abodes; 
and the rivalry of the males in many kinds prevents 
their crowding the one on the other. Whether the 
swallow and house-martin return in the same exact 
number annually is not easy to say, for reasons 
given above ; butit is apparent, as I have remarked 
before in my monographies, that the numbers re- 
turning bear no manner of proportion to the num. 
bers retiring. 
—————s 
LETTER XXXVI. 
Selborne, June 2, 1778. 
Dear S1r,—Tue_ standing objection to botany 
has always been, that it is a pursuit that amuses 
the fancy and exercises the memory, without im- 
proving the mind or advancing any real knowledge; 
and, where the science is carried no farther than a 
mere systematic classification, the charge is but 
too true. But the botanist that is desirous of wi- 
ping off this aspersion should be by no means con- 
tent with a list of names; he should study plants 
philosophically, should investigate the laws of ve- 
getation, should examine the powers and virtues of 
efficacious herbs, should promote their cultivation, 
and graft the gardener, the planter, and the hus- 
bandman on the phytologist. Not that system is 
by any means to be thrown aside—without system 
the field of Nature would be a pathless wilderness 
—but system should be subservient to, not the main 
object of, pursuit. 
Vegetation is highly ane of our attention, 
2 
