Comments on JD's work in photography; JH goes on to talk about JH's ideas of 'chemical' rays of light.
Comments on JD's work in photography; JH goes on to talk about JH's ideas of 'chemical' rays of light.
Sends CW a specimen of JH's 'mercurial photographic process.' JH is pleased that W. H. Fox Talbot received the Rumford medal.
Is anxious for some means to be developed to get a measurable quantity [preferably by weight] from the action of a beam of light on a surface. JH has been experimenting in photography with 'flouric' compounds.
Sends description and drawings of JH's actinoscope. Requests estimate for time and expense of constructing it. Questions about clock mechanism and prisms.
Regrets that GD cannot build JH's entire actinoscope. If GD can make at least mechanical components, JH will supply optics and clockwork. Can GD complete these [by end of March]? Funds are limited; please estimate cost.
Confirms scale of drawings [for JH's actinoscope]. Has found simple contrivance to replace clockwork. Will order lenses and prisms from Munich; all English glass has color aberrations.
Finished the reductions of all of the nebulae and double stars recorded at Cape Town; JH soon hopes to prepare for the publication of his Cape Results.
Sends RH a packet of photographs with a description of each type.
Read John William Draper's papers; although he believes that Draper's instruments are inconsistent, JH feels that they are still important because they are measurable. Decries [L. F.] Moser's skepticism of photography's value, calling it a 'blindfolding to some of the most interesting physical relations that have ever been discovered.'
JH mislaid the request for specimens of photography, but now sends them; describes those sent. Explains how to get a copy of JH's paper on photography.