From:
William Selwyn
To:
Sir John Herschel
Date:
[11 January 1862]
Source of text:
RS:HS 15.468
Summary:
Discusses a depression on a heliograph, which he cannot reconcile with [Frederick] Howlett's observations. Conjectures over-exposure in printing may be the culprit.
Contributor:
John Herschel Project