MR. CUNDELL’S PROCESS. 291

these solutions are about to be applied to the iodized paper, theyare to be mixed together, in equal volumes, by means of agraduated drachm tube. This mixture is called“the gallo-nitrate of silver.” As it speedily changes, and will not keep formore than a few minutes, it must be used without delay, and itought not to be prepared until the operator is quite ready toapply it.

9." The application of this“ gallo-nitrate” to the paper is amatter of some nicety. It will be found best to apply it in thefollowing manner:— Pour out the solution upon a clean slab of

late-glass, diffusing it over the surface to a size corresponding tothat of the paper. Holding the paper by a narrow upturnedmargin, the sensitive side is to be applied to the liquid upon theslab, and brought in contact with it by passing the fingers gentlyover the back of the paper, which must not be touched with thesolution.

10. As soon as the paper is wetted with the gallo-nitrate, itought instantly to be removed into a dish of water; five or tenseconds at the most is as long as it is safe at this stage to leavethe paper to be acted upon by the gallo-nitrate; in that spaceof time it absorbs sufficient to render it exquisitively sensitive.The excess of gallo-nitrate must immediately be washed off bydrawing the paper gently several times under the surface ofwater, which must be perfectly clean; and being thus washed,it is finished by drawing it through fresh water, two or threetimes, once more. It is now to be dried in the dark, in themanner described in§ 7; and, when surface-dry, it may either beplaced, while still damp, in the camera, or in a portfolio, amongblotting-paper, for use. If properly prepared, it will keepperfectly well for four-and-twenty hours at least, preserving allits whiteness and sensibility.

11. The light of a single candle will not injure the paper at amoderate distance; but the less the paper, or the excitingsolution, is unnecessarily exposed, even to a feeble candle-light,the better. Common river or spring water answers perfectly towash the paper, distilled water being required for the silversolutions only.

Stains of gallo-nitrate,” while recent, may be removed fromthe fingers by a little strong ammonia, or by the cyanide of

otassium.

The third process is that of

12. The Exposure in the Camera , for which, as the operatormust be guided by his own judgment, few directions ean begiven, and few are required. He must choose or design his ownsubject; he must determine upon the aperture to be used, and