Instructions for preparing liquid for the actinometer. Describes 'very strange' experiments on the spectrum as well as an 'unusual' cloud formation.
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Instructions for preparing liquid for the actinometer. Describes 'very strange' experiments on the spectrum as well as an 'unusual' cloud formation.
Proposes meeting times in town. Suggests that JF observe the upcoming total eclipse astronomically. Agrees with JF's seemingly 'cold &c' circular on scientific partnerships, while regretting that it needed to be written.
Sets up approximate meeting time, depending on his family's timely departure to Antwerp, with JF at the R.S.L. apartments.
Compares actinometric measurements of radiation. Explains interest in total eclipse relative to actinometry. Discusses the possibility of making actinometric measurements by photographic means.
Received JF's paper on 'thermographic process.' Believes that thermic rays were responsible for experimental results of JF, J. W. Draper, and Ludwig Moser. JH's theory of and experiments with thermic rays, which are different from 'calorific' and visible rays, in solar spectrum.