Instead of pyrogallic acid solution, I have, for some time past, at the suggestion of Dr. Vogel, employed the ordinary developer for the purpose of intensifying negatives. This is prepared of

Sulphate of Iron......................................................................

50 grammes.

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

30 "

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

1000 "

Or, instead of the above amount of sulphate, seventy grammes of the double sulphate of iron and ammonia may be used.

The silver solution, used in equal proportion with the above, consists of

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

20 grammes.

Citric Acid,..............................

30 "

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

1000 "

K. Schwier.

145. Very closely allied with this is the consideration of what is the best means of giving that reinforcement to the negative which is sometimes necessary to furnish full printing power. I have before laid down the axiom that, given collodion, bath, developer, light, and operator, all of the best, the negative will possess, at the first intention, the proper printing qualities, with merely addition, and often not even that, of a drop of silver to the developor; but in practice, we all know, you cannot always have this combination of excellences, and then the negative, not possessing sufficient intensity, reinforcement becomes desirable; and the object of this part of my note is to point out once again the importance of letting this be the result of coloration rather than piling up by silver. A negative having its printing' times, of course, when all these will have to be resorted to in order to save a negative which cannot be replaced. But, as a rule, the exposure should be so carefully timed so not so require and reinforcing of the negative whatever.

146. Then are times, too, when, by under - exposure or unavoidable circumstances of light, the negative is too dense and harse, thus producing not only results harsh and hard in tone and color, but producing them with a slow unwillingness to the printer. It is well, power by the first development, or by coloration, looks, when varnished, as smooth and bright as the glass itself; white intensification by silver causes it to have a clouded appearance, partly smooth and partly tough.

Mr. Lacy employed the solution of iodide of potassium and bichloride of mercury, poured on and off alternately, and his pictures have been equalled by very few; hut, unluckily, a change takes place in negatives thus intensified by the light, and the negative gradually loses its details and becomes flat and poor. But a far better effect is produced, and no after change takes place, when a solution of the two in combination is employed. Prepare it thus: Take a saturated solution of bichloride of mercury, and add a ten-grain solution of iodide of potassium. A dense vermilion precipitate of iodide of mercury is seen, and the potas--ium is to be added carefully until this precipitate is exactly redissolved. This is very important. If too much potassium is present, this negative has a yellow tinge given, which is liable to change under solar influence; but with the exact quantity of each a very rich printing color is given. It may be kept in a dropping - bottle, and about ten drops in an ounce of water will do a dozen half - plate negatives. A peculiarly valuable printing quality is given by this means, and the increase is so gradual that special parts are readily brought to higher intensity or less, as desired. - Samuel Fry.

My practice, for many years past, has been to so manage my light that I had no occasion to intensify the negative, for I have long held an opinion that the most perfect results could only be obtained from a negative on which no deposit of silver, other than that which came in the ordinary course of development, was permitted to take place. It has frequently happened that, in consequence, I have created difficulties for myself which a little denser deposit of silver on the negative would have entirely removed. The results, on the whole, have been so much more to my taste, and the difficulties so easily ramoved by an intelligent management of the paper in printing, that I have been well content to go on in the same way. Of course, it would be quite impossible, expcept at the present time of year, to employ a bath of one hundred grains per ounce, and get from the negatives I have indicated the best proof possible; for though the deposit is comparatively thin on the negative, the contrast of light and shade is greater than that formed in the generality of negatives now produced. Over - exposure would be fatal to my method of working. - Valentine Blanchard.

146. A secondary exposure of the sensitive plate to light before development. I also find, will enable mo to make a passable picture where the exposure in the camera has been unavoidably too short To effect this, I prefer opening the shutter of the dark-slide within about three feet of an ordinary fishtail burner which I have fixed in the dark a few seconds' exposure will cause a slight fogging of the negative, which, in the case of a subject presenting strong contrasts, will cause the resulting prints to appear softer and more pleas therefore, to have a means at hand for correcting this evil also. Various methods of doing it are given further on, to which refer in time of need. 147. Varnish. - To protect the delicate film from injury while printing, the negative must be varnished with something like the following:

Alcohol..........................................................................................

28 ounces.

GumCamphor,............................................................

1/2 ounce.

Oil of Lavender,............................................................

1/2 "

Brown Shellac Gum,............................................................

2 ounces.

Gum Sandarac,............................................................

2 drachms.

These ingredients are placed, in a bottle, in a vessel of hot water over the tire, until the gums are dissolved. Occasional stirring should be given, and finally the whole filtered before use. Before the varnish is applied, the last trace of the fixing solution must be washed from the film.

ing. Of course care and judgment must be used throughout, and the intensifying of the negative must be done with due discretion. As the gaslight is practically a fixed quantity, after a few trials it is easy to cause just the amount of fogging necessary for removing the hard, bare patches in an otherwise good negative. - Alfred Hughes.

A method of reducing the strength of negatives proposed by Mr. Letalle promises to be of much value for other purposes than a mere reduction of an over-dense negative, the process being one that may be termed suggestive. He operates as follows in the case of pictures that have been under-exposed and over-developed so as to force out the shadows: The negative, after having undergone all the ordinary operations, is cleaned and washed, remarking the want of harmony or too much opacity. He pours upon it quant, suff. of a solution of fifteen grains of chloride of gold in one pint of water. This is poured alternately from the negative into a glass, and from the glass on to the negative till the picture is properly darkened. He then washes and pours on a corner of the negative sufficient nitric acid to cover it. The whole of the silver of the negative is dissolved instantly, and the picture appears to be totally gone. On washing it carefully there is left in the texture of the collodion, however, an image, exceedingly delicate, of reduced gold. This picture can be intensified with the greatest facility by means of sulphate of iron, in the first instance, the picture coming forth with the greatest transparency, the mezzotint more intense, and the high-lights remaining transparent; or by means of pyrogallic acid, in the second instance, the primitive connection between the mezzotint and the high-lights being the same, and the advantage in this case lying in the ability to check the reinforcement on this side of the first, carried on too much. The golden, delicate picture which remains after the use of the nitric acid seems very excellent for enlargements by the solar camera, on account of its great transparency and delicacy. - J. Traill Taylor.