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Letters, Announcements, fyc. 
XXVI,— Letters, Announcements, fyc. 
The following letters, addressed “To the Editor of r The 
Ibis/ ” have been received :— 
Sir, —In f The Ibis * for 1862 (p. 183) the Editor, in re¬ 
viewing a paper by Herr Meves “ On the Red 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. E. 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, Ee 2 0 3 ). 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 (sesquiferrocyanide 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 
