which the transfer is to be effected, such piece of paper or card having been previously moistened with water, and I press the print and mount strongly together; and, after the paper or card has become perfectly dry, I remove the paper or other supporting material, temporarily attached, previous to development, either by simply tearing it off, where the cement used in the temporary mounting is of a nature to allow of this without injury to the print, or I apply to the temporary mount, benzole or turpentine, or other solvent of the cement employed, or I immerse the print in such solvent, and then detach the temporary mount, and so expose the reverse surface of the print; and, after removing from the surface of the print, by means of a suitable solvent, any remains of the cement used in the temporary mounting, I finish the print by pressing in the usual manner. If, however, the print be collodionized, and be required to be tinted with water-color, I prefer to remove the collodion film from the surface of the print, and this I do by the application of ether and alcohol.
“Having now set forth the nature of my invention of ‘Improvements in Photography,’ and explained the manner of carrying the same into effect, I wish it to be understood, that under the above in part recited letters-patent, I claim: First, the preparation and use of colored gelatinous tissues in the manner and for the purpose above described.
“Secondly, the mounting of undeveloped prints, obtained by the use of colored gelatinous tissues, in the manner and for the purpose above described.
“Thirdly, the re-transfer of developed prints, produced, as above described, from a temporary to a permanent support.”It will be seen that one of the essential features of the process is the production of a “tissue,” which renders the manipulations necessary to perfect results practical and easy, which were before difficult or impossible. We shall see in the historical notes which follow that the principles upon which carbon printing is based had received partial recognition at an early period. As they became more perfectly understood the practical difficulties seemed greater. The imperative condition upon which half-tone depends, the exposure of one side of the
