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the paper which bears the corresponding number to be placed in the camera obscura.

"(2) Method of Fixing the Images.-After having tried ammonia, and several other reagents, with very imperfect success, the first thing which gave me a successful result was the iodide of potassium, much diluted with water. If a photogenic picture is washed over with this liquid, an iodide of silver is formed which is absolutely unalterable by sunshine. This process requires precaution; for if the solution is too strong, it attacks the dark parts of the picture. It is requisite, therefore, to find by trial the proper proportions. The fixation of the pictures in this way, with proper management, is very beautiful and lasting. The specimen of lace which I exhibited to the Society, and which was made five years ago, was preserved in this

manner.

"But my usual method of fixing is different from this, and somewhat simpler, or at least requiring less nicety. It consists in immersing the picture in a strong solution of common salt, and then wiping off the superfluous moisture, and drying it. It is sufficiently singular that the same subject which is so useful in giving sensibility to the paper should also be capable, under other circumstances, of destroying it, but such is, nevertheless, the fact.

"Now, if the picture which has been washed and dried is placed in the sun, the white parts color themselves of a pale lilac tint. after which they become insensible. Numerous experiments have shown to me that the depth of this lilac tint varies according to the quantity of salt used, relatively to the quantity of silver. But, by properly adjusting these, the images may, if desired, be retained of an absolute whiteness. I find I have omitted to mention that those preserved by iodine are always of a very pale primrose yellow; which has the extraordinary and very remarkable property of turning to a full gaudy yellow whenever it is exposed to the heat of a fire, and recovering its former color again when it is cold.

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A curious incident must be recorded here. On March 14, 1839, Sir John F. W. Herschel read before the Royal Society a "Note on the Art of Photography, or the Application of the Chemical Rays of Light to the Purposes of Pictorial Representation." In this paper Herschel states that he was unaware of what Fox Talbot had done, but hearing of Daguerre's discovery he had devised several processes for obtaining similar photographic records. He exhibited twenty-three photographs, made on chloride of silver and fixed in sodium thiosulphate, one taken through a lens and the rest copies of engravings and drawings (see Royal Society Proceedings, 1837-1843). Herschel, it may be added, had written a paper on the thiosulphates, in the Edinburgh Philosophical Magazine for 1819, p. 8. Few records of Talbot's further experiments occur until February 19, 1841, in a letter to the

W. J. Mullins.

editor of the Literary Gazette, and published in The Philosophical Magazine, vol. 19 (1841) p. 90. In this he announces his discovery of a latent image, and in a paper to the Royal Society on the following June 1oth, fully describes the process. We quote first from his letter of February 19th:

"One day, last September, I had been trying pieces of sensitive paper prepared in different ways in the camera obscura, allowing them to remain there only a very short time, with the view of finding out which was the most sensitive. One of these papers was taken out and examined by candle light. There was little or nothing to be seen upon it, and I left it lying on a table in a dark room. Returning some time after I took up the paper and was very much surprised to see upon it a distinct picture. I was certain there was nothing of the kind when I had looked at it before; and therefore (magic apart) the only conclusion that could be drawn was, that the picture had unexpectedly developed itself by a spontaneous action. Fortunately I had recollected the particular way in which this sheet of paper had been prepared, and was, therefore, enabled immediately to repeat the experiment. The paper, as before, when taken out of the camera, presented hardly anything visible; but this time, instead of leaving it, I continued to observe it by candle-light, and had soon the satisfaction of seeing a picture begin to appear, and all the details of it came out one after the other."

In his paper before the Royal Society (Royal Society Proceedings, 1841, and Philosophical Magazine, vol. 19, (1841, p. 164) Talbot describes this development process in detail. It is the calotype process. We give the staple of it:

Preparation of the Paper.-Take a sheet of the best writing paper, having a smooth surface, and a close and even texture.

The water-mark, if any, should be cut off, lest it should injure the appearance of the picture. Dissolve 100 grains of crystallized nitrate of silver in six ounces of distilled water. Wash the paper with this solution, with a soft brush, on one side, and put a mark on that side whereby to know it again. Dry the paper cautiously at a distant fire, or else let it dry spontaneously in a dark room. When dry, or nearly so, dip it in a solution of iodide of potassium containing 500 grains of that salt dissolved in one pint of water, and let it stay two or three minutes in this solution. Then dip it into a vessel of water, dry it lightly with blotting-paper, and finish drying it at a fire, which will not injure it even if held pretty near, or else it may be left to dry spontaneously.

All this is best done in the evening by candle-light. The paper, so far prepared, the author calls iodized paper, because it has a uniform pale yellow coating of iodide of silver. It is scarcely sensitive to light, but, nevertheless, it ought to be kept in a portfolio or a drawer until wanted for use.* It may be kept for any length of time, without spoiling or undergoing any change, if protected from the light. This is the first part of the preparation of calotype paper, and may be performed at any time. The remaining part is best deferred until shortly before the paper is wanted for use. When that time is arrived,

*Talbot afterwards found it an advantage to sun the iodized paper.-EDS.

take a sheet of the iodized paper and wash it with a liquid prepared in the following manner:

Dissolve 100 grains of crystallized nitrate of silver in two ounces of distilled water; add to this solution onesixth of its volume of strong acetic acid. Let this mixture be called A.

Make a saturated solution of crystalized gallic acid in cold distilled water. The quantity dissolved is very small. Call this solution B.

When a sheet of paper is wanted for use, mix together the liquids A and B in equal volumes, but only mix a small quantity of them at a time, because the mixture does not keep long without spoiling. I shall call this mixture the gallo-nitrate of silver.

Then take a sheet of iodized paper and wash it over with this gallo-nitrate of silver, with a soft brush, taking care to wash it on the side which has been previously marked. This operation should be performed by candle-light. Let the paper rest half a minute, and then dip it into the water. Then dry it lightly with blotting paper, and finally dry it cautiously at a fire, holding it at a considerable distance therefrom. When dry, the paper is fit for use. The author has named the paper thus prepared calotype paper, on account of its great utility in obtaining the pictures of objects with the camera obscura. If this paper be kept in a press it will often retain its qualities in perfection for three months or more, being ready for use at any moment; but this is not uniformly the case, and the author therefore recommends that it should be used in a few hours after it has been prepared. If it is used immediately, the last drying may be dispensed with, and the paper may be used moist. Instead of employing a solution of crystallized gallic acid for the liquid B, the tincture of galls diluted with water may be used, but he does not think the results are altogether so satisfactory.

(To be continued.)

A

A FEW SUGGESTIONS.

BY E. M. MILLER.

MATEURS wishing to try color screen work, should use a glass screen. The cell, containing a variable solution, is all right for experts, but for beginners it will prove difficult, and, like the stops of a camera, lead to endless useless experiments. In isochromatic landscaping, stick to a one-colored screen, and one stop, preferably f/8. I use a Poco glass screen, and find it satisfactory.

So far I have used none but the Cramer isochromatic plate. The medium plate is best in all cases except when the wind is blowing, when, of course, the rapid plate and short exposure is preferable. I think in exposures of equal effect the rapid plate is more likely to fog by halation. Possibly the proper thing to do is

to back the plate; but I prefer to work out the problem on unbacked plates.

To get landscapes with clouds one must learn thoroughly the lens, the screen, and the plate. The fewer the variations the more likely will one be successful. My theory is that the exposure should be longer than that given by rule, and the development be slow, made so by a weaker developer and a retarder. I think I can recommend a few experiments that for the beginner will be a short cut to desirable ends. The makers of the color screens give a rule for exposure, generally three times the exposure without screen. We will suppose the exposure, stop f/8, to be sec, then with screen it will be 1 sec. Now add one second and consider the correct exposure to be 2 sec.

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First decide your under-exposure, say I sec.= A; then at the third withdrawal of slide, or when whole plate is uncovered, an exposure of one second is given. Then to give 2 sec.-the normal exposure-B must 1 sec. so that A + B = 24. Now C,being the first exposure,must be such that A+B+C 4, or 1 sec. In other words, you withdraw the slide and expose 1 seconds; a second

=

and expose 1 seconds; and when the slide is

out, expose one second; this gives the desired result. The diagram is very convenient for figuring each exposure. You simply figure it out backwards.

The greatest care must be taken not to move the camera; and for this reason a cap exposure is preferable. A few such exposures will teach a beginner more as to the correct exposure for his lens and screen than he ever could learn by reading.

In development, a slow reducer is preferable. I have tried pyro, metol, and tolidol, and have concluded they were too rapid. I think the best developer is eikonogen or eiko-hydro. The results of my experiments lead me to combine my developer with more water and less alkali (or potash) than the usual formulae, and I use the retarder. I make up 10 per cent. solutions of common salt, bromide of potash, and persulphate of ammonia. To about 7 ounces of developer I add about 6 drops of the bromide or salt, and I drachm of the ammonium persulphate phate I rather think the salt is preferable as it seems to combine chemically less rapidly with the persulphate than the bromide. This

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can be proven by adding half drachm salt and half drachm bromide, each to I drachm of the persulphate.

In the developer the ammonium persulphate decomposes slowly; therefore the developer should be used fresh, and not over four plates developed in one batch of developer.

For the best results the sun should be shining on the landscape; that is, do not expose while the sun is even slightly clouded. Remember the effect of bright sunlight on a plate is altogether different through a color screen than without one. Through a screen the bright light is very much reduced in its effect on the plate. The finest pictures are to be had early in the morning or late in the evening, while the sun is shining, and large broken masses of clouds are in the sky.

One of my amateur friends complained he could not get good gradation in color screen work. Possibly he under-exposed. I get better gradation than in ordinary exposures. Very likely, he missed, not gradation, but sharp definition. The color screen seems to diffuse defini

tion-a decided advantage in landscape work. An important point is when to stop development. The ordinary rules will hardly hold in this work. A plate very much undeveloped will give black shadows; over-developed, clouds that will not print. There is a point in development when the image begins to fade, and a point when it disappears. It is my opinion that development should stop half way between these points. An easy experiment will greatly assist in determining when to stop. Expose at the same time, same exposure, three plates. Fix one when the image becomes black; one when it begins to fade; and one about half way between. Use for all three the same developer.

If any photographer doubts the addition of the retarder to the developer is a benefit, let him try the following experiment. Expose three plates alike. Develop one without retarder; then add 6 or 8 drops of the bromide or salt and develop the second plate. Finally add I drachm of the ammonium persulphate and develop the third plate. I think the results will prove my method correct.

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The "Clove" is a name given to the series of small artificial lakes, made by damming a stream which runs through the valley of that name. Their use seems to have been to supply waterpower for operating grist and saw mills in prerevolutionary days; but they are now used as içe ponds in winter, and as rendezvous for picnic parties in summer.

The stream heads in a swamp near the Clove pumping station, south-east of Richmond Turnpike, and a short distance west of the Clove Road. It is easily reached by either the "Richmond Turnpike" or "Silver Lake car of the Staten Island Electric R.R. Co., from St. George.

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There are three lakes in all, each being at a lower level than the preceding one, and separated from it by a stretch of the stream itself. The entire distance covered, some mile and a half, is replete with many a picturesque bit well worth an attempt at capture.

The first lake commences on the north side of Richmond Turnpike, about an eighth of a mile west of the Clove Road, and extending in a north-westerly direction. On the west side is a path which runs the entire length of the valley, and affords a convenient means of access. This lake was apparently formed by excavating the stream-traversed swamp, and building a dam at the lower end, thereby forming a shallow basin. Below the dam may still be seen the remains of the "Brittain Grist-Mill,"

The left bank, looking down the lake, is somewhat marshy and heavily wooded, while the right is cleared land on which are situated an ice house, stable, etc. There is nothing particu

larly interesting here, the pretty bits being found lower down.

Proceeding onwards the valley narrows considerably; the sides becoming steeper and well wooded. In places the small trees almost meet overhead, and are reflected in the quiet waters of the slow-moving stream, while the sunbeams stealing through the fretwork of the branches and leaves give touches, here and there, of brilliant light, greatly adding to the charm of the scene.

Soon after this we came to a place where the valley again widens out, and the stream forms the second lake. The banks here are considerably steeper than those of the first lake. At this place several pretty pictures may be taken, while the dam at the lower extremity of the basin is very picturesque, especially when there is water falling over it.

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Below the dam is the

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