_C._--To sixteen ounces of Plain Collodion add from eight to twelve drops of tincture of iodine (50 grains of dry iodine dissolved in half an oz. of alcohol) and 14 grains or drops of fluoride of ammonium; shake the mixture well; then add all of the solution _B_; shake it again and thoroughly; after this has stood for twenty-four hours it can be used, but will be found better after it has been prepared one week. Nitrate of Silver Solution. Pure rain or distilled water 64 ounces. Nitrate of silver (in crystals) 4-1/4 ounces. Clean pure white sugar 75 grains. Six grains of iodide of ammonium dissolved in half a drachm of alcohol. The above, thoroughly mixed and allowed to stand for a few hours, should be filtered through a new clean sponge, asbestos, or Swedish filtering paper, and then a few drops of nitric acid, chemically pure, should be added, just enough to redden blue litmus-paper; then it is ready for use, and will improve by age. _Developing Solution._--This formula has proved very satisfactory in my hands, and I hope will be equally so with all who give it a trial:-- Water 1 pint. Boracic acid 3/4 ounce. Protosulphate of iron 3/4 ounce. Pulverized nitre 1/2 ounce Three drops of oil of cinnamon dissolved in two ounces of alcohol. Dissolve and filter, and it is ready for use. It is better to make this developer fresh every other day. _Dissolving off the Iodide of Silver._--Water, about half a pint; cyanide of potassium, enough to clear the impression in about thirty seconds--say a quarter of an ounce. _Fixing the Impression._--I use the article well known to every good photographer as Humphrey's Collodion Gilding, and it serves the purpose better than anything that I I know of. _Black Varnish._--I generally purchase this from the dealer; but I have made an article which answered the purpose well, by dissolving pulverized asphaltum in spirits of turpentine. Any of the black varnishes can be improved by the addition of a little bees'-wax to it. It is less liable to crack and gives an improved gloss. _Negative and Printing Processes._--Being myself an amateur, and desiring to study economy and convenience, my attention has been given to the test of numerous plans for avoiding the necessity of two baths and silvering solutions and I feel confident that the amateur will find the following, in connection with the foregoing Positive Process, the best adapted to his wants.