Letter to Richard Guy Ash about dicyanine
From The Arthur Conan Doyle Encyclopedia
My dear Ash
I hope you will soon be quite all right again. The rest will do you no harm. If I could only break my leg I think it would be the saving of me.
I've lost all heart over dicyanine, but your explanation that the Germans made it up differently would give a great starting point. At present I can get us result with any screen, dark & light or carmine. Your little lot has vanished altogether.
Yours very sincerely
A Conan Doyle.
- Source: Brian Pugh Collection.