1851 Great Exhibition: Official Catalogue: Class X.: Griffiths and Le Beau
404. GRIFFITHS and LE BEAU, 15, Coborn Road, Mile End.
Daguerreotype portraits and pictures, with electrotype copies taken from them.
[The daguerreotype picture being produced by a film of mercury upon a silvered plate, there is necessarily an irregularity over its surface. If a plate thus prepared is connected with a galvanic battery, and placed in a solution of sulphate of copper, the copper precipitated on the surface receives a most delicate impression of the daguerreotype image. In addition to the differences produced by the varying thickness of the mercurial film, there is not unfrequently a slight difference in the colour of the copper deposited over those parts thickly coated with mercury, and those over which the silver is exposed.— R. H.]