From:
John Henry Dallmeyer
To:
Sir John Herschel
Date:
[24 September 1866]
Source of text:
RS:HS 6.2
Summary:
Outlining phenomena in the refraction of light. Has been experimenting with wide angle lenses for cameras and gives some of their defects. Would like JH's opinion on how to get rid of the 'secondary focus.'
Contributor:
John Herschel Project