Leaf of a Plant.
Hitherto we have presented to the reader the representations of distant objects, obtained by the use of a Camera Obscura. But the present plate represents an object of its natural size. And this is effected by quite a different and much simpler process, as follows.
A leaf of a plant, or any similar object which is thin and delicate, is laid flat upon a sheet of prepared paper which is moderately sensitive. It is then covered with a glass, which is pressed down tight upon it by means of screws.
This done, it is placed in the sunshine for a few minutes, until the exposed parts of the paper have turned dark brown or nearly black. It is then removed into a shady place, and when the leaf is taken up, it is found to have left its impression or picture on the paper. This image is of a pale brown tint if the leaf is semi-transparent, or it is quite white if the leaf is opaque.
The leaves of plants thus represented in white upon a dark background, make very pleasing pictures, and I shall probably introduce a few specimens of them in the sequel of this work: but the present plate shews one pictured in the contrary manner, viz. dark upon a white ground: or, speaking in the language of photography, it is a positive and not a negative image of it. The change is accomplished by simply repeating the first process. For, that process, as above described, gives a white image on a darkened sheet of paper: this sheet is then taken and washed with a fixing liquid to destroy the sensibility of the paper and fix the image on it.
This done, the paper is dried, and then it is laid upon a second sheet of sensitive paper, being pressed into close contact with it, and placed in the sunshine: this second process is evidently only a repetition of the first. When finished, the second paper is found to have received an image of a contrary kind to the first; the ground being white, and the image upon it dark.