The method of silvering the paper with ammonio-nitrate of silver, is as follows: take a tuft of clean cotton, roll it into a ball-shape, then wet it by holding it against the mouth of the bottle containing the ammonio-nitrate, and when well wet, apply it to the paper (which should be placed flat on a clean board) by gently rubbing it over the surface, care being taken not to roughen it. If the solution has not been filtered for some time, it would be advisable to pour a little on the centre of the paper, and then distribute it over the surface by means of the cotton, which is held in the fingers: by this last method any sediment which may be in the bottom of the bottle is prevented from getting upon the paper, and causing spots. I have used a brush for the purpose of distributing the solution, by which plan there is less liability of getting it on the fingers and staining them. Care must be taken to cover the _entire surface_ of the paper, or there will be light streaks, occasioned by the absence of the silvering solution. This want of silver will appear on the paper in light parts, as seen in the accompanying cut: [Illustration: Fig. 36.] After the paper has been perfectly coated, or washed with the silvering solution, it should be placed in a perpendicular position to dry. I usually tack the paper on a board of the requisite size, and then stand it on one edge until it has drained and dried. As soon as dry, it is ready for use. This paper will not keep more than twelve hours, therefore the operator should silver in the morning the quantity required for the day. It is imperatively necessary that the silvered paper be kept in the dark. It is extremely sensitive to light, and a very brief exposure of the prepared sheet would render it unfit for use. Printing the Positive. The several kinds of apparatus used for holding the negative and the sensitive paper together, have already been given on page 36, Figs. 31, 32, 33. The paper having been salted and silvered, as just described, should be placed on the pad of the printing frame or glasses, with its sensitive surface up, and then the negative placed directly upon and in contact with it; then it is to be fastened together, when it will be ready for exposure to the direct rays of the sun. From 10 to 40 seconds will be found enough to give a sufficiently intense print. The paper first changes to a slate color, and then to a brown or copper color t when of a dark slate color is about the proper time to take it out and immerse in the toning bath. Fixing and Coloring Bath. I have employed the proportions given by Mr. Hardwich in his _Photographic Chemistry_, page 209--Humphrey's American edition. Solution of chloride of gold, a quantity equivalent to 4 grains. Nitrate of silver 30 " Hyposulphite of soda 2 ounces. Water 8 "