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SCIOPTICON MANUAL. 75 portrait negatives. There seems no reason why enlarge- ments made in this way, for ornamental transparencies, to be hung in the window, or set in a frame, should not become a profitable branch of photography. The toning of glass positives, to be used for orna- mental purposes, involves some thought as to the par- ticular color, or shade of color, that will suit the picture best; and it is impossible to give one process that will suit all tastes alike; some having a preference for black tones, others for blue-black, brown, or the various shades of gray. A detailed description of the manner of pro- ducing these various tones would require too much space, and is so simple that no one can go astray. The principal chemicals required are: Chloride of gold, bichloride of platinum, bichloride of palladium, sulphide of potassium, and permanganate of potassium; in all cases use singly and very dilute. I am disposed to consider chloride of palladium as the most reliable chemical that has come under my notice. Its action is perfectly manageable, easy to prepare, will not stain, and gives uniformly good results. The toning solution that I use is made as follows: Add six drops from the stock-bottle of chloride of palladium to each ounce of water; this solution should be of a delicate straw color. No other manipulation is required. After the plate has been developed and fixed, wash as usual, then apply the toning solution by flowing it over the plate similarly to the developer. Its action will be quick, giving a black tone to the positive. Wash well, dry, and varnish if desirable. Thcso transparencies are covered and bound with an opal or ground-glass, or they may be flowed with a var- nish containing a little fine zinc paint, ground in varnish. It may bo mentioned in this connection, that artists