OF SELBOBNE. 
247 
Ever since I have attended to the subject of ornithology, 
I have always supposed that that sudden reverse of affection, 
that strange oc]^t la-ropy 7i which immediately succeeds in the 
feathered kind to the most passionate fondness, is the occa- 
sion of an equal dispersion of birds over the face of the 
earth. Without this provision, one favourite district would 
be crowded with inhabitants, while others would be desti- 
tute and forsaken. But the parent birds seem to maintain 
a jealous superiority, 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 swallows and house martins return in the 
same exact number annually is not easy to say, for rea- 
sons given above ; but it is apparent, as I have remarked 
before in my Monographies, that the numbers returning 
bear no manner of proportion to the numbers retiring. 
LETTER XL. 
TO THE HONOURABLE DAINES BARRINGTON. 
Selborne, June 2, 1778. 
HE 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 wiping 
off this aspersion, should be by no means content with a list 
of names; he should study plants philosophically, should 
investigate the laws of vegetation, should examine the 
powers and virtues of efficacious herbs, should promote their 
cultivation ; and graft the gardener, the planter, and the 
husbandman on the phytologist. IN'ot that system is by 
any means to be thrown aside — without system the field of 
