262 ON THE CLASSIFICATION OP BIRDS. 
equally valuable : they forget that the rarity of an 
object constitutes its current value, and that in propor- 
tion as more are brought into the market, so does their 
value diminish. At the sale of BuUock^s museum, very 
many of the humming birds sold for as many guineas 
as they can now be purchased for shillings. It is our 
duty to guard individuals from incurring severe losses, 
although it is to the interests of science that these 
materials for our study should be cheap and abundant. 
We know of two instances where a whole museum of 
animals, &c. has been purchased at the Cape of Good 
Hope, under the idea tliat its sale in England would 
realise a large profit ; when, after being exhibited in 
London, and subsequently sold, the proceeds have 
hardly covered one-half of the original purchase. There 
are persons again, in India, New Holland, Tortola, 
Eio de Janeiro, and other stations, who trade in these 
objects, and they are purchased by persons returning 
to England, under the supposition of their selling to 
advantage. Such speculators will generally be greatly 
deceived. Our supplies exceed the demand. There 
are, comparatively, few persons as yet who form regular 
collections of birds ; for if they are fond of ornithology, 
they can see what specimens they desire at the public 
museums, now formed, or forming, in all the great 
towns of England. The directors .or managers of 
these latter, again, depend chiefly on donations for 
adding new specimens to their collections ; the funds 
devoted to this object, if any, being generally very 
trifling. Hence it happens that large collections, for 
which no purchasers can be found, are generally sacri- 
ficed at auctions, or sold to the dealers for about one- 
third their value.. Desirous, therefore, as we must be 
to encourage the importation of ornithological speci- 
mens, for the greater diffusion of knowledge, we yet 
cannot hold out any other object that they will accom- 
plish. Large collections of cpmmon American birds are 
now frequently sold at an average of two shillings a 
skin ; a sum which is probably much less than their 
