To Osbert Salvin 1 November 
Down, | Beckenham, Kent.
My dear Mr Salvin
How good you have been. I have been very glad to see the 2 specimens, especially the Merganetta, for as far as fitness for sifting is concerned, it is a capital link between the Shoveller & common duck. I could hardly have desired a better; & so is in some slight degree the Aix.1 I soaked the heads for an hour or two, & now they are drying on my table.2 & tomorrow or day after I will send them to station. Thanks to you, I have worked out my case far better than I ever dreamed of doing
Yours very sincerely | Ch. Darwin
P.S. I will send the Box off to night by our Carrier. to London & by Deliverance Coy to you.— Carriage paid whole way.— I think this safer than Railway.—
He appreciates the two specimens [skins of Mergenetta and Aix sponsa], especially the Mergenetta, which as far as sifting is concerned, is a capital link between the shoveller and the common duck. Arrangements for their return.