78 BIRDS OF NORFOLK. 



a simple chemical test, Herr Meves ascertained that 

 the ferruginous tint in the plumage of these birds is 

 owing to " a superficial deposit of oxide of iron on the 

 feathers," a similar stain on the eggs arising from the 

 same cause. The same peculiarity observed in some of 

 the feathers of the crane, in Jemtland, he also found to 

 be caused by the presence of iron, and from these data, 

 the editor of the " Ibis" suggested that similar experi- 

 ments should be made on the rufous-tinged feathers of 

 the whooper and Bewick's swan. To this end being 

 desirous of establishing the point on unquestionable 

 authority I solicited the assistance of my friend Mr. 

 F. Kitton, of Norwich, whose name is so well known in 

 connection with microscopic investigations, and having 

 placed in his hands the head of a very adult mute 

 swan, strongly tinged with ferruginous matter, he has 

 furnished me with the following most satisfactory result 

 of his investigations: "As I anticipated," he writes, 

 " the colouring matter is iron (peroxide Fe 2, O 3.) On 

 testing some of the deeply stained feathers from the 

 head with ferro cyanuret of potassium the characteristic 

 deep blue colour immediately appeared (sesqui ferro- 

 cyanide of iron.) On placing white feathers 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 certain localities 

 where swans are known to exhibit this rufous colouring 

 most vividly, and I may here add that the delicate buff 



