My Dear Mr Talbot,
I thank you very much for your kind Note of the 22d April, <1> and the sketch of the Browning Herschel Spectroscope. <2>
I have received from Paris a specimen of Riffaults process called Heliography <3>, or Sun-etching, upon Steel. It is a Copy of a very beautiful drawing by Guignet, <4> and it is impossible to distinguish it from a crayon drawing. It is 13 inches long and 8 broad, and is sold at M. Rapilly's 3 Quai Malaquais.
My friend says that the specimens sell at a fabulous price, in consequence of the secret being kept by Madam Riffault the Artists Widow. Riffault is said to have spent his fortune, and lost his life on perfecting the Invention. It is applied to copying drawings by the old Masters.
I should like much to see how your process <5> deals with a photographic copy of a crayon drawing. I presume it would be exactly the same as the one I have described.
I am, Ever Most Truly yrs
D Brewster
Allerly Melrose
May 4th 1865
Notes:
1. Not traced.
2. A meteor spectroscope of which Sir John Frederick William Herschel (1792–1871), astronomer & scientist was one of the designers. See Astronomy Magazine, November 1990.
3. Claude Félix Abel Niepce de Saint-Victor invented a process for making photomechanical printing plates by using sensitised asphalt (very similar to the original work of his uncle, Nicéphore Niépce. However, the plates were too weak to print from. Pauline Riffault made plates using this process, which were then engraved by hand by Adolphe Pierre Riffault, from which prints for sale were produced. The subjects included portraits of royalty and zoological specimens.
4. Adrien Guignet (1816–54), French painter.
5. Photoglyphic engraving.