I have fallen back on a modification of the old wet process, borrowing from different workers the formula employed. The bath, which should be sunned and filtered before adding the acids, is composed of

Silver Nitrate,........................................

1/2 ounce.

Water,........................

10 drops

Nitric Acid,........................

3 drops

Acetic Acid,........................

12 "

The plates are coated with a ripe collodion, being first rubbed with French chalk, and immersed for at least five minutes. I develop in a glass - bottomed dish with the following:

Pyrogallic Acid,........................

30 grains.

Citric Acid.......

1 drachm.

Acetic Acid,......

2 drachms.

Alcohol,.......

2 "

Nitric Acid,........................

7 drops.

Water,........................

10 ounces.

and fix with hyposulphite of soda. The developer acts slowly, so that density and detail are and the whole sealed together by means of a border or binding of black needle-paper.

354. There are several other methods besides the "wet" of producing these beautiful pictures. The "wet" is easiest because most like the ordinary work of the photographer, but, by means of it, a film is given well under control; and, as lantern slides often require strong contrasts, this is an advantage. Another advantage of this developer is, that it yields a pleasing tone at once without requiring the after application of chloride of gold, etc., which is necessary when the pictures are developed with iron. The transparencies are best taken in the camera, and, with ordinary care and judgment, this process will reward the operator with very good specimens. - Rev. B. Holland.

I always make the sulphuret solution a deep orange color and filter before using, as the same strength does not answer for every sample of collodion. I test by pouring on a plate, not wishing it so strong that it will in a second or so turn black, but it should take several seconds, sometimes longer, before the stain is deep enough. It is deep enough when bluish, then pour off the solution (do not use the same again), carry the plate into the strong light; looking through, watch its action. "When it has passed the gray-blue it gradually deepens; when just purple douse it under the tap. If the action is carried any further, it becomes a deep sepia, which will flatten the picture; when a dark-blue, or what will appear on the 6creen solid black, is wanted, stop the toning at the gray - blue, and wash. When the positives are overtimed, it is impossible to get any other than a sepia tone. When under-exposed, they are hard. New collodion not too thick makes the best positives, as they have not that solidity that ripe collodion gives. Very old collodion has some of the same properties of new, but the action of time is very slow, yet good results can be obtained. The action of sulphuret of potassium as a toning agent is peculiar, as it makes translucent what otherwise would remain smoky or a mass of black shadow. .For reproducing negatives, the toning is omitted. Place the negative in position, varnish side out; give time until full detail is obtained with a quick development; fix with cyanide of potassium. While wet place the positive in the place of the negative, face outward, and expose less than one half of the previous exposure by ordinary development. By this means a negative can be reproduced nearly equal to the original. - W. L. Shoemaker.

354. Transparencies upon collodion cannot match those on albumen in any way. The film is so fine that even in the deepest shadows there is a transparency, and, as it were, detail, which would have been blocked out or lost in a collodion film, not to speak of the rich tone which can be given to an albumen positive with very little pains. Although not so rapid as collodion, they will give transparencies superior to the other. I will now treat the subject fully: 1. The dark - room; 2. Preparation of albumen; 3. Cleaning and polishing the plate; 4. Coating the plates with albumen and drying; 5. Sensitizing; 6. Exposure and developing; 7. Toning.

The first subject requires the most care. The dark-room must be very small, the ceiling and the walls painted in oil, the floor laid with marble or slate slabs, a large sheet of plate-glass fixed to serve as a table, a kind of a cupboard with levelled glass shelves, and as few chemicals as possible. This is what the dark-room must contain in order to prepare albu-menized plates with any degree of certainty. Dust is the greatest enemy of this admirable process, and it is the first to be vanquished, that is why I advise a small room. The walls, ceiling, and floor are so arranged that they can be washed now and then to take off the which is not nearly so delicate and structureless as that obtained by the albumen or emulsion process. Hints as to both of these are given in the notes - as will enable any tasteful manipulator to secure dust. The drying cupboard is made of varnished zine, as in Fig. 100. a, plate - glass shelves the same width as the cupboard, but an inch and a half shorter; the first shelf touches the zinc on the right-hand side; the second shelf touches the zinc cupboard on the left-hand side, and so on, alternately, to the top of the cupboard. On the right-hand side of the bottom of the cupboard is a hole, B,over which is soldered a piece of fine wire - gauze, covered with a piece of fine linen. This hole is an inlet for air, and the fine linen acts as a filter to stop dust and dirt from entering with the air. It would be well even to dip the linen into a little glycerin, and change it now and then. On the left - hand side of the top is another hole which forms outlet 0; this is covered by a piece of sheet-iron piping, in the interior of which is placed a Bunsen burner, d. The prepared plates having been laid upon the glass shelves, the doors, E E are closed. The Bunsen burner lighted, a draught is established in the chimney, and fresh air is drawn through hole, B, which, following the arrows, Fig. 101, passes over the surface of all the plates and dries them very quickly; if the air be very damp, it can be made to pass through chloride of calcium. In fact, it can now be seen that to succeed with this process great cleanliness is required, and above all, great care not to open doors too rapidly, or go in and out of the dark-room too frequently, so as to raise the dust. I dwell very long upon this subject, being certain that this is one of the greatest stumbling-blocks in the process.