Believes that the operative rays in JH's thermographic process are neither 'calorific' nor 'thermal'.
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Believes that the operative rays in JH's thermographic process are neither 'calorific' nor 'thermal'.
Some information about Charles Piazzi Smyth. JH needs information about some of RH's photographic paper, which JH has tried but without success.
Sorry to hear RH has been ill; JH sends some photographic examples.
Thanks for RH's paper on mineralogy. JH has explored use of mercury together with iron in photography.
Sends RH a packet of photographs with a description of each type.
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.
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.'