From:
William Henry Fox Talbot
To:
Sir John Herschel
Date:
[5 April 1843]
Source of text:
RS:HS 17.316
Summary:
Comments on JH's positive calotype. Suggests comet may be return of (J.-D.) Cassini's comet of 1668. Gives theorem for finding parabolic orbit of comet if two observations are made in the ecliptic.
Contributor:
John Herschel Project