Exchanging further information on several aspects of the photographic process [see RH's 1840-4-15].
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Exchanging further information on several aspects of the photographic process [see RH's 1840-4-15].
Has not lately done much work in photography, except to work with paper treated with vegetable substances.
RH's experiments are extremely interesting and deserve to be pursued. Comments on experiments made by Michael Faraday and others relating to the formation of crystals in a magnetic field and the effect such crystals have on polarized light.
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.
Thanks RH for a sample of Daguerreotype paper. Comments on some aspects of the action of 'thermic' rays and 'chemical' rays in photography.
Does not know anywhere that such processes as RH uses are used for registry work, although the idea is frequently raised.
Thanks for RH's paper on mineralogy. JH has explored use of mercury together with iron in photography.
Thanks RH for his 'extensive and instructive view on the present state of photography.' Found many interesting results in experimenting with vegetable substances. Surprised by RH's discovery that bi-chromate of potash is a photographic substance; JH nearly achieved this result.
Some information about Charles Piazzi Smyth. JH needs information about some of RH's photographic paper, which JH has tried but without success.
Believes that the operative rays in JH's thermographic process are neither 'calorific' nor 'thermal'.
Clarification of priority to the prismatic analysis of the Daguerreotype photograph; comments on the location of a limiting diaphragm in a camera obscura.
Will forward RH's paper to the R.S.L.; intrigued by RH's results using mercury vapor to produce the image on exposed paper.
Unable to give any specifics concerning Louis Jacques Mandé Daguerre's new photographic process. Discovered that old paper specimens produced a much better representation of the spectrum in its natural colors than those obtained at the date of JH's paper; these results are 'light on a dark ground,' which makes JH more hopeful that colored photography will someday be perfected. Has experimented with vegetable substances.
Sends RH a packet of photographs with a description of each type.
Some comments about photographic processes and about RH's observations of the heavens [see RH's 1843-3-24].
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.'
Sorry to hear RH has been ill; JH sends some photographic examples.
Comments on RH's chromatype photographic process and other processes tried by JH.
Hopes that his paper does not anticipate any of RH's work; will share with the R.S.L. any of RH's results. Laments that he is unable to fix the spectral colors on photographic paper. Asks if RH has studied the bromines.
Expresses his pleasure at RH's new position at the Museum of Economic Geology.