X 



198 OBSERVATIONS ON THE CHANGES OF 



describe the process by which they are effected, has been a source of 

 much perplexity to naturalists and philosophers. In Europe, Cuvier, 

 Temminck, Yarrell, Drs Flemming and Whitear, Mr Montagu, and 

 several writers in the recent numbers of the journals of Paris, Dres- 

 den and Halle, have indulged in various speculations, and adopted a 

 number of contradictory theories. Some have contended that birds 

 moult but once, others twice a year ; some that the annual mutations 

 are produced by a gradual fading or brightening of the feathers ; whilst 

 others have contended that it is produced by a sudden moult. Dr 

 Flemming, who adopts the theory that the feathers of birds do not ar- 

 rive at maturity and drop off till they are a year old, supposes that 

 those feathers which are received in spring, remain till the following 

 spring, and that those added in autumn, moult on the succeeding au- 

 tumn, thus making two irregular moultings in a year. One school of 

 naturalists has supposed that the change in those quadrupeds which 

 become white in winter, is effected by the gradual lengthening and 

 blanching of the summer fur; whilst another presumed that this won- 

 derful mutation can only occur by a shedding of the summer hair, 

 which is replaced by the snowy pelage of winter. In our own country, 

 few observations have been made on this subject. Our celebrated or- 

 nithologists, Wilson, Bonaparte and Audubon, appear to have dwelt 

 very sparingl}'^ on the changes of plumage in birds, which, however 

 overlooked, seems to belong to their department ; and, with the excep- 

 tion of a paper by Mr Ord, in the Transactions of the American Phi- 

 losophical Society, I do not recollect having read any article on this 

 department of the physiology of birds and quadrupeds. In our inves- 

 tigations of nature, we are perhaps too prone to build our theories first, 

 and afterwards seek for the facts which are to support them. Hence, 

 naturalists, having the same field of inquiry before them, and reading 

 from the same book of nature, which is open to all, are very apt to be 

 swayed by their preconceived notions, and thus retard the progress of 

 science by unprofitable disputes. 



The time perhaps has not yet arrived, when any certain theory can 

 be built on this part of physiology. A sufficient number of experi- 

 ments and observations have not been made with care and judgment; 

 nor have such a body of facts been collected as will enable us to judge 



