6th. Mounting of the Print and Separation from the Glass.—As soon as dry the print may be retouched, if necessary. This retouching must be done by looking at it by transmitted light. To mount it I paste, by means of gelatine, one or more sheets of white on very light tinted papers or cardboard on the print, taking great care to remove all air-bubbles which may be entrapped between the paper and the moist glue. I place it under pressure, and leave it for twenty-four hours; then I cut the edges loose with a penknife, and leave it exposed to the air; when in a short time the paper spontaneously detaches from the glass, the print adhering firmly to it.
When the paper used has a proper tint in harmony with the subject, and with the carbon and Magenta color of the print, it has all the appearance of a varnished oil painting.
The author liberally offers any more information on the subject to all who desire it.
Note.—Notwithstanding this process is a little laborious, and more adapted for amateur performance than for the regular profession, it contains so many practical hints that it was thought its publication might be of benefit to those who desire large carbon prints.
SWAN'S ACTINOMETER.
Before proceeding to manipulatory details, it is desirable to mention the mode of meeting another serious difficulty which has hitherto stood in the way of carbon printing. As the film of bichromated gelatine and carton is black, there is no darkening during exposure to indicate the progress of printing. No perceptible change is made in the film by the action of light.
In the uncertainty arising from this circumstance it has been necessary to guess the exposure, or estimate it by a consideration of the strength of the light and the
