206 NATURAL HISTORY OF SELBORNE. 



in some of the lowest and meanest thatched cottages. Now as 

 these eight pairs, allowance being made for accidents, breed 

 yearly eight pairs more, what becomes annually of this increase ; 

 and what determines every spring which pairs shall visit us, and 

 reoccupy their ancient haunts ? 



Ever since I have attended to the subject of ornithology, I 

 have always supposed that that sudden reverse of affection, that 

 strange avruTTopyrj, which immediately succeeds in the feathered 

 kind to the most passionate fondness, is the occasion 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 destitute 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. Whe- 

 ther the swallows and house-martins return in the same exact 

 number annually is not easy to say, for reasons 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 HON. DAINES BARRINGTON. 

 DEAR SIR, Selborne, June 2, 1778. 



THE standing objection to botany has always been, that it is a 

 pursuit which amuses the fancy and exercises the memory, with- 

 out improving the mind or advancing any real knowledge : and, 

 where the science is carried no further 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 philo- 

 sophically, should investigate the laws of vegetation, should 

 examine the powers and virtues of efficacious herbs, should pro- 

 mote their cultivation ; and graft the gardener, the planter, and 

 the husbandman, on the phytoiogist. 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 subser- 

 vient to, not the main object of, pursuit. 



Vegetation is highly worthy of our attention ; and in itself is 



