Page:Proceedings of the Royal Society of London Vol 4.djvu/145

Rh of perfection, a process for copying the forms of natural objects by means of solar ligbt, which is received upon paper previously pre- pared in a particular manner. He observes, that a prior attempt of this kind is recorded in the Journal of the Royal Institution for 1802; by which it appears that the idea was originally suggested by Mr. Wedgwood, and afterwards experimented on by Sir Hum- phry Davy. These philosophers found, that their principle, though theoretically true, yet failed in practice, on account of certain diffi- culties ; the two principal of which were : first, that the paper could not be rendered sufficiently sensible to receive any impression what- ever from the feeble light of a camera obscura ; and secondly, that the pictures which were formed by the solar rays could not be pre- served, owing to their still continuing to be acted upon by the light.

The author states that his experiments were begun without his being aware of this prior attempt ; and that in the course of them he discovered methods of overcoming the two difficulties above re- lated. With respect to the latter, he says, that he has found it pos- sible by a subsequent process, so to fix the images or shadows form- ed by the solar rays, that they become insensible to light, and con- sequently admit of being preserved during any length of time : as an example of which, he mentions, that he has exposed some of his pictures to the sunshine for the space of an hour, without injury.

With respect to the other point, he states that he has succeeded in discovering a method of preparing the paper which renders it much more sensitive to light than any which had been used previ- ously ; and by means of which he finds, that there is no difficulty in fixing the pictures given by the camera obscura and by the solar microscope.

He states that in the summer of 1 835 he made a great number of portraits of a house in the country of ancient architecture, several of which were this evening exhibited to the Society.

After some speculations on the possibility of discovering a yet more sensitive paper, the author mentions, that the kind employed by him may be rendered so much so, as to become visibly affected by the full light of the sun, in the space of half a second.

The rest of this paper contains an account of various other ways in which this method may be employed in practice, according to the kind of object which it is required to copy : also, a brief mention of the great variety of effects resulting from comparatively small differ- ences in the mode of preparation of the paper : and, of certain ano- malies which occur in the process, the cause of which has not hitherto been rendered distinctly manifest.

In conclusion, the author designates this as "a new process, which he offers to the lovers of science and nature."