276 , Letters, Announcements, SfC. 



XXVI. — Letters, Announcements, S^c. 

 The following letters^ addressed " To the Editor of * The 

 Ibis/ '^ have been received : — 



Sir,— In 'The Ibis' for 1862 (p. 183) the Editor, in re- 

 viewing a paper by Herr Meves " On the lied Colouring in 

 Gypaetus," suggested that the chemical test by which he 

 ascertained that the ferruginous tint in the plumage of certain 

 specimens of the Lammergeier were owing to a " superficial 

 deposit of oxide of iron on the feathers/' should be applied as 

 well to the rufous-tinged feathers of the Whoopers and Be- 

 wick's Swans. Acting on this hint, I placed, recently, in the 

 hands of Mr. F. Kitton, of Norwich, well known in connexion 

 with microscopic investigations, the head of an adult male 

 Swan, strongly tinged with ferruginous; and the following is 

 the result of his investigations : — 



"As I anticipated/' he writes, *^the colouring-matter is 

 iron (peroxide, FegOg) . On testing some of the deeply stained 

 feathers from the head of the Swan with ferrocyanuret of 

 potassium, the characteristic deep blue colour immediately 

 appeared (sesquifcrrocyanide of iron) . On placing white fea- 

 thers from the neck in contact with some red-crag debris and 

 water, they acquired a pale buff tint ; and these became blue, 

 like the red feathers of the head, when treated with the ferro- 

 cyanuret of potassium. I afterwards mounted some of the 

 tested feathers in Canada balsam, and examined them with 

 the micro-spectroscope, and found that the spectra of the 

 originally and experimentally stained feathers were identical. 

 I think you are correct in your surmise that the rufous tint 

 is produced by contact with ferruginous sand." 



It remains now only to test the water and the subsoil in 

 localities where Swans are known to exhibit the rufous colour- 

 ing most vividly ; and I may here add that the delicate buff 

 tint on the white feathers placed by Mr. Kitton in water in 

 contact with red crag, is particularly interesting, as it cor- 

 responds exactly with the colouring so often remarked on the 

 necks of domestic Swans, just so far as they are usually sub- 

 merged in feeding, occasioned more probably by the water 



