each case the recognition of the fact upon which the loss of half-tone was based, seems to have been the result of independent observation. Having applied a thick coating of the sensitive gum and carbon to his paper, he noticed, after exposure, that “the outer crust was more sunned and hardened than the inner,” and that, by the time the paper was sufficiently steeped, the inner surface, which had been least sunned, was too soft, and was washed away, carrying with it the “outer crust.” It occurred to him, therefore, that if he could get the inner surface rendered insoluble first, he could overcome the difficulty. He accordingly attempted to print through the coated paper, so that the inner surface was acted upon first, leaving the soluble portions on the outer surface to be removed by washing. This gave a certain amount of success; but the exposure was long, and the print looked granular from the texture of the paper through which the light passed. Subsequently, he tried the use of waxed paper as a support for sensitive material. This lessened the exposure, and in some degree lessened the granulation; but the lights, consisting of waxed paper, were not good in color, and certain practical difficulties remaining, the method did not come into general use. The principle of securing half-tone in carbon prints was now known, but an efficient and practical mode of applying it remained unknown. To the subsequent modes of utilizing this principle, we shall refer presently.
Towards the close of 1859, M. Joubert called attention to a process of carbon printing which he styled phototype. An example, published in the journal of the Photographic Society, in June, 1860, showed that the process possessed much promise of excellence, the results far surpassing anything till then seen. That they could be printed with facility in large numbers was
