588 Retrospective Criticism. 



prospect, he will approach his object, study its geological 

 structure ; and, instead of bringing home a series of merely 

 pretty views, he will have to offer a valuable tribute to science. 

 Almost every science has its signs ; and I trust that 

 Messrs. Murchison, Buckland, De la Beche, Sedgwick, Lyell, 

 Greenough, Conybeare, &c., will feel that geology, which 

 ranks in importance with the highest, ought no longer to be 

 without them. — J, Byerley, London^ April 29. 1832. 



Art. V. Retrospective Criticism, 



Facts and Observations in Natural History y communicated by Mr. Sells, 

 the publication of which, in this Number, was promised in p. 470. of the 

 last, must stand over until the next Number. — J. D. 



On Birds oiling their Plumage. — Sir, In answer to Mr. Waterton, " On 

 birds using oil from glands, for the purpose of lubricating the surface of 

 their plumage," and particularly with regard to the following paragraph 

 (p. 414.), I send you some remarks on a tame dove : — " Suppose, for sake 

 of argument, that the bird does actually employ oil from the gland to 

 lubricate the plumage (which, by the by, I flatly deny), how is the head 

 and part of the neck to be so supplied with oil ? Why, the truth is, they 

 never can be supplied ; and if you examine, with the nicest scrutiny, the 

 feathers of the body which come within the range of the bill, and the 

 feathers of the head, which are out of the range of the bill, and then com- 

 pare them, you will not observe the smallest difference in their downy 

 appearance : proof positive that the plumage of the body has not been 

 lubricated with oil from the gland." — No proof at all. Last summer, I 

 brought up, by hand, a turtle dove, which I accustomed to fly about my 

 room, till within this last month, at all times, except at night. InvariaJDly, 

 when I had it sitting on my hand, it would begin pluming itself (particu- 

 larly while in moult, which it was for about four months), and, at such 

 times, it was curious to see it apply its bill to the gland or nipple just 

 above its tail, and, by pinching it, procure something (though I could 

 never discover what) ; on withdrawing its bill, it always stretched out its 

 neck, and twisted its head about in the strangest manner, with its eyes 

 shut, and the bill opening and shutting, as if the act of chewing something 

 which put it in pain, but which, I always considered, was for the purpose of 

 spreading, or allowing the substance procured to circulate to all parts of the 

 bill : this operation lasted about twelve seconds, and then it immediately 

 applied it, very quickly, to only three or four different parts of its plumage 

 at a time, and, at its pleasure, easily enough, all over its head and neck, by 

 rubbing them on such parts as were within a convenient distance (for 

 who ever saw a bird, particularly a duck, wash itself, without observing it 

 rub its head and neck on its back, or the shoulders of its wings ?) : this I 

 have seen it do at least ten times in as many minutes, on my hand ; but 

 confess I could never detect what it was it procured from the gland for 

 the purpose of spreading over its plumage, though I could distinctly see it 

 pinch the nipple, as it would allow me to remove the feathers while in the 

 act. Yours, &c. — H, Henslow. St. Albans, June 14. 1832. 



Stormy Petrels taken in the Interior of the Island. — Sir, I have before 

 now heard the remark made, that if one were to enumerate all the birds to 

 be met with in any district, or even parish, it would be quite surprising to 

 see how full and extensive a catalogue might by this means be supplied; 

 especially if the district selected for the purpose, in the first instance, be 



