187. Permanganate of potash is much used, but concerning it, one thing, however, can bo said, namely, that it lacks force in its operations upon a negative, does not thicken, as it were, bo intensification. Their are many methods of procedure in this line, some acting "with the delicacy of a jeweller's tool, while others possess the power of a veritable sledge. Thus all sorts of effects are obtainable.

188. As will be observed, some methods of intensification secure only a change in color of the negative, while with others an actual chemical change is caused in the films. Experience will teach the manipulator but merely changes the color of the deposit. This, I have found, can be entirely obviated by adding bichromate of potash. My formula is:

1.-Permanganate of Potash,..........................................

5 grains.

Water......................................................................

1 ounce.

2. - Bichromate of Potash,..........................................

10 grains

Water........................................................

1 ounce.

These solutions are made up and kept separate, being mixed in equal proportions when wanted. It is exceedingly useful for intensifying a negative of a baby which has been much under-exposed, or for enlarged copies or negatives of line engravings for silver printing or photo-lithography. The improved intensifier is used after fixing, and after the negative is strengthened and washed it should be flowed with a solution of gum-arabic. In some instances it is not advisable to varnish, but print with care without varnishing. - David Duncan.

I claim to have originated this intensifier. The formula is as follows:

1.Hydrochlorate of Ammonia,........................................................

1 ounce.

Bichloride of Mercury,........................................................

1 ounce.

Distilled Water,........................................................

20 ounces

2. - Chloride of gold,........................................................

1 grain.

Distilled Water,Distilled Water,................................

1 drachm.

To make the intensifier, put two drachms of each solution into a four-ounce bottle and fill up with water. A small quantity of this should be poured rapidly over the negative, from a glass measure, and kept moving upon the surface in the usual way until the necessary density is obtained. If it has lost its yellow color, and become white when returned into the glass, it should be thrown away, and the operation, if incomplete, must be continued with fresh solution. I may add that there is yet another and not unimportant merit in this intensifier. A small quantity applied to the film of a well-exposed and fully developed negative will enable you to view the portrait through the glass, and then it has the appearance of a very delicate and beautifully shaded positive, thus permitting the sitter to judge at once of the likeness, expression, etc. In the case of a very thin negative, the intensifier may be followed by a weak solution of iodide of potassium - half a grain to an ounce of water. - J. A. Winter.

188. Perchloride of iron is a salt easily obtainable in commerce. It is very deliquescent, very cheap, and a little goes a long way. My method of using it is thus: I make a stock solution of, say, ten or twenty grains to the ounce of water. This makes a dark, cherry-colored solution. At the time of using I add a few drops of this solution to an ounce of water in a measure-glass. This dilute solution should not be darker than a pale golden tint. I pour it over the well-«7&ahed plate and watch the change. In a few seconds the deposit forming the high-lights changes very slightly from its drab color to a pale ashy hue. 1 then wash it off well, and which to choose in time of need. Knowing how far the negative in hand comes from being desirable in every way, he must select the means of recovering it which will be the surest, as he would select a tool were be a mechanic. The perchloride of iron, perhaps, acts,with most certainty and is the easiest to manage, though it is largely a matter of choice.

next pour over the hypo, solution used for fixing. This dissolves away the thin layer that has changed color, I wash well again and examine the negative to observe if sufficient deposit has been removed. If it has, the operation in complete; if it be still too dense, I repeat the operation with the perchloride and the hypo, as before, well washing between the operations. If the perchloride be too strong, or has been left on too long, the negative will be found to have been reduced too much, and recourse must be had to the usual intensifying process to recover what has been lost. This, however, is Dot nearly so desirable as reducing only to just the desirable extent. I should mention that this method leaves the silver in a spongy state that is easily penetrated by the varnish; it is better, therefore, rather to under than overdo this reduction, otherwise the negative, when varnished, will be too weak in the high - lights. I rarely reduce my negative by only one operation of the perchloride and hypo., but I generally use the solutions alternately two or even three timet, and thus gradually approach my result, it being very difficult, especially if there be much density, to exactly estimate the influence of the perchloride solution. In this method it is best to experiment on a useless plate or two. At first most persons will either carry the process of reduction too far, or will not carry it far enough. I know few processes requiring more judgment in use than this one, but it is really at times so useful that all photographers should be acquainted with it. By its employment many otherwise useless negatives may be made to produce passable prints. It can be used advantageously to reduce the intensity of a negative in local parts. It may be poured on hands or foreheads, shirt-fronts, white skirts, or similar parts that are relatively too dense. I use a dropping - bottle with a fine orifice, and, holding it close to the plate, pour on a fine stream to just where I want to localize the effect, washing instantly the solution away before it sesibly acts on the adjoining parts. This I repeat two or three times in succession, washing between, when I have a small part - say the side of a face, hands, white gloves, or handkerchief - prior to using the fixing agent. - Jabez Hughes. The ferridcyanide of potassium system is also very valuable, but the chemicals are rather more difficult to obtain. I had often admired the negatives produced by Dr.Maidstone