A Manual Of Photography

284 PRACTICE OF PHOTOGRAPHY. suggested the process I am about to describe has been claimed by Messrs. Havell and Wellmore, and also by Mr. Talbot; indeed, there appears no reason to doubt the originality of either of these gentlemen, Mr. Havell having prosecuted his experiment in ignorance of the fact that Mr. Talbot had used the same means to diversify his photographic specimens. Mr. Talbot proposes that a plate of warmed glass be evenly covered with a common etching ground, and blackened by the smoke of a candle. The design is then to be made, by carefully removing from the glass all those parts which should represent the lines and shadows, and shading out the middle tints. It will be evident that the light passing through the uncovered parts of the glass, and being obstructed by the covered portions, will impress on the white photographic papers a correct picture, having the appearance of a spirited ink drawing. Mr. Havell's method was to place a thin plate of glass on the subject to be copied, upon which the bigla lights were painted with a mixture of white lead and copal varnish, the proportion of varnish being increased for the darker shading of the picture. The next day, Mr. Havell removed, with the point of a pen-knife, the white ground,to represent the dark etched lines of the original. A sheet of prepared paper having been placed behind the glass, and thus exposed to light, a tolerable impression was produced; the half tints had, however, absorbed too much of the violet rays, an imperfection which was remedied by painting the parts over with black on the other side of the glass ; if allowed to remain too long exposed to the sun's rays, the middle tints became too dark, and destroyed the effect of the sketch. Another method employed by Mr. Havell was to spread a ground composed of white lead, sugar of lead, and copal varnish, over a plate of glass, and having transferred a pencil drawing in the usual manner, to work it out with the etching point. Various modifications of these processes have been introduced by different artists, and they evidently admit of many very beautiful applications. When the etching is executed by an engraver, the photograph has all the finish of a delicate copper- plate engraving. The only thing which detracts from this method of photography is, that the great merit of self-acting power is abandoned. Section VI.—Albuminized Paper. M. Le Gray gives the following as the improved proportions in which lie recommended an albuminous mixture to be made for paper.