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Negretti & Zambra in correspondent 
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From:
Negretti & Zambra
To:
Sir John Herschel
Date:
[3 June 1863]
Source of text:
RS:HS 13.147
Summary:

Have made several of JH's actinometers but have always experienced difficulty with the fluid, ammonia sulphate of copper. Can some other fluid be used? They are now making two actinometers for a foreign observatory and would like to make them as accurate as possible.

Contributor:
John Herschel Project
Document type
Transcription available