its specific gravity, will sink in the water. Have three pails side by side, each nearly full of rain-water. As soon as a second plate is ready, take hold of the first plate, in a horizontal position, collodion side downward, give it a sort of undulatory motion, but very gently, and then transfer it to the second pail, and place it against the side of the latter in an inclined position as before. The second plate is now removed from the bath, and after draining, is put in the first pail. The process is the same when the third plate is ready; the first, being treated as before, is removed to the last pail, the second plate is immersed in the middle pail, whilst the first pail becomes again empty for the reception of the next plate.

Finally, the first plate is flowed several times with fresh distilled water, which thus removes every trace of free nitrate of silver, as well as of the nitrates of the metals, produced by decomposition.

Flowing the Plates with Tannin.

The plates, thus thoroughly and carefully washed, are flowed with the following solution :

Dissolve over night, and then filter through a wet filter two or three times; finally, add one drachm of alcohol if the tannin has to be kept some time.

Flow the plate with this solution, and allow the superfluous quantity to pass off at one corner into a wide-mouthed vial. Now flow the plate several times, and collect the residual quantity in the stock-bottle. Drain and rear on one corner on a piece of glass covered with bibulous paper.

Some photographers wash the tannin film before drying; we have not tested this plan sufficiently to pronounce an opinion about it; but prefer adherence to a mode which invariably is successful.

The room in which the plates are thus prepared may be maintained moderately warm, so that the film may dry spontaneously, and not very slowly. After each plate has stood for ten minutes or longer, there will be an accumulation of tannin solution on the blotting-paper. It is now well to remove the plates to fresh blotting-paper, and to prepare the wet supports, with fresh pieces of blottingpaper, for other plates. If this precaution be not observed,

streaks and stains are apt to manifest themselves on the pendent corner when the film is submitted to the developing solution.

When thoroughly dry, the tannin-plates are now ready for exposure, or for piling away in their proper receptacle, the dry-box plate-holder, or a dark cupboard.

Exposure of Tannin Plates.

The time of exposure naturally depends upon a variety of contingencies, such as the intensity of light, the time of the day, the season of the year, the climate, and the power and working properties of the lens. With one of Harrison and Schnitzer's globe-lenses, stereoscopic size, and smallest aperture, in the month of April, in the State of New-York, an exposure of from eight to twelve seconds will produce a very satisfactory negative. In December and January, during the extreme cold weather, from thirty to forty-five seconds were found necessary. Where the circumstances permit, it is well to give at least a sufficient exposure, and even a little too much is no injury, because the development is quite under control; for where the exposure has not been sufficiently long, a picture can be obtained, it is true, but it is too harsh, it is all black and white; there are none of those intermediate or middle tints that characterize a true artistic picture.

Development of Tannin Plates.

This is the treatment which deviates entirely from what has hitherto been practiced. After exposure, the plates are returned to their dark receptacles, in which they remain until required for development. We are not prepared to say how long the time may be between exposure and development without being in any way prejudicial to the latter operation. This time is somewhat indefinite, as long as the film is preserved in an obscure place, and free from moisture and deleterious effluvia.

The plate for development is first carefully moistened. with distilled water, slightly warmed in winter, that is, of a temperature of about 60°. The film is then covered with the following solution:

Alkaline Developer for Tannin Plates.

Saturated solution of carbonate of soda,

30 minims.

4 drachms.

Alcoholic sol. of pyrogallic acid, (10 gr. to the oz.,) 6 minims.

The saturated solution of carbonate of soda is prepared in the following manner: To four ounces of water add car

bonate of soda as long as it is dissolved; finally leave a quantity in the bottle for a day or longer, and shake the mixture occasionally. Finally filter and preserve.

The solution of pyrogallic acid is also kept in stock, and made by dissolving twenty grains of the acid in two ounces of alcohol.

Mix quickly, and immediately pour it upon the moistened plate. If the time of exposure has been nearly right, the image will soon begin to appear, and although faint and of a slightly reddish hue, will proceed until all the parts have appeared. Do not be alarmed about the faintness of the picture; as long as all the traits are distinct, the negative will afterward come out quite right. Wash the film carefully, and then proceed to the next step.

Intensifying of the Image in the Tannin Process. Prepare, in the first place, the following solutions in stockbottles:

From No. 1 take one drachm, and add seven drachms of water. This solution is for present use. According to the size of the plate, pour a sufficient quantity of this solution into a small wide-mouthed vial, flow the film with this solution, and then pour it back again into the vial. Now add, for a stereoscopic plate, about six drops of the nitrate of silver solution from stock-bottle No. 2, shake the mixture, and again pour it upon the film. The traits will soon darken, and the image finally will reach an intensity adapted for the printing process. It sometimes happens, however, when the exposure has been too long, or from other causes, that the image begins to be obscured by an incipient fogging; when this evil manifests itself, throw off the intensifier, wash the plate thoroughly, and fix in the ordinary fixing solution of hyposulphite of soda. The image is again washed, and the intensifying process can now be prolonged until the desired effect is obtained.

If we had used the old acid developer with the time of exposure indicated, it would in most cases fail to bring out a negative image. The alkaline developer will be put to the test the coming summer; we shall then know positively

whether instantaneous photographs can be taken by the dry process.

WET COLLODION PROCESS WITH THE ALKALINE DEVELOPER.

The author has not yet had time to test the merits of this process, which is recommended by very high authority, the editor of the Photographic Notes. He asserts that a negative can be produced by means of the alkaline developer in about the same time as is generally given for an ambrotype, within doors of course. As far as our experience goes in these matters we should be inclined to doubt the practicability of this process with an ordinary acid silver bath, that is, the successful practicability; and we would recommend all photographic artists that feel inclined to try this new process, to prepare a neutral bath of pure ingredients according to the formula in the preceding article. In addition to the instructions, set forth for the first time in the journal just alluded to, it seems to us to be necessary to prepare the plates previously with a coating of gelatine, albumen, or some other transparent medium, on which the collodion film is afterward superposed, and by which this film is prevented from peeling off in the subsequent treatment of development and fixing. In this case the plates are first well cleaned and then coated with a film of bromo-iodized gelatine, as recommended in the preceding process for the preparation of dry plates. This work can be performed in the evening, or at times when there is no hurry of business.

cess.

A good bromo-iodized collodion is requisite for this proFirst drive off the moisture from each plate, already gelatinized, allow it to cool, and then flow with the collodion in the usual manner, and sensitize to a distinct cream color. The plate is then subjected to washing, as in the dry-plate process, and left in a grooved box filled with distilled water till required for use. In this way a stock of plates is prepared early in the morning, and put away in water for use during the day.

When a customer arrives, the necessary position is assumed in focus, and a plate is then taken out of its groove, flowed with distilled water, and then with the following solution:

The solution is first filtered through wet filtering paper two or three times, and then poured upon the collodion film backward and forward, as is the common practice with

dry plates. The plate is then allowed to drain for a moment, and finally fixed in the plate-holder. The utmost precaution is required here to keep the corners of the shield perfectly free from nitrate of silver, which, if present, will inevitably stain the plate to a large extent all along from each corner by a sort of capillary attraction.

Exposure.

The time of exposure for a negative beneath a good skylight, Sutton says, will be about as long as is required for a glass positive. This time varies according to a variety of circumstances, which the practitioner has to learn by experience. After exposure the plate is taken into the darkroom and flowed with distilled water; it is next submitted to the developing process.

Alkaline Developer for Wet Plates.

To four ounces of water add forty grains of carbonate of soda, shake frequently, and, after a number of hours, filter the solution through paper into stock-bottle No. 1.

Secondly, dissolve twenty grains of pyrogallic acid in two ounces of alcohol, filter and preserve in stock-bottle No. 2.

Whenever an image has to be developed, prepare each time a fresh developer as follows, (for a card-picture :)

Water,

Soda solution, from No. 1,
Pyrogallic solution, from No. 2,

4 drachms.

30 minims.

15 minims.

Shake quickly and then cover the exposed collodion film with the mixture. If the time of exposure has been somewhat near right, the image will soon begin to appear; the latter has a faint reddish color, if the conditions are correct. As soon as all the traits of the picture are out, although still quite faint, the development may be regarded as complete. It is of no great consequence, however, if the developer be left upon the film for an indefinite time; no injury is thereby produced, so that, as regards this part of the business, when the proper time of exposure is once known, the plates can be left in the developer and other business in the mean while attended to.

The next part of the process consists in strengthening and darkening the traits of the image already visible. This is denominated the

Intensifying of the Image.