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FIG. 5. Centrifugal force experiment. First position.
Without hesitation throw the arm in the air, and swing it, not too quickly, but without shaking it, in the direction of the arrows in the diagram (Fig. 6).
FIG. 6. Swinging the glass.
FIG. 7. The action completed.
After one complete revolution the glass should be as shown by Fig. 7; whilst in this position it may be placed on the table. At first it is advisable to practice this experiment with water, but, as more skill is acquired, other liquids, such as milk or wine, may be used as occasion permits.
FIG. 8. The spoon mirror.
A NOVEL MIRROR
A simple method of illuminating the back of the mouth and throat, especially when throat trouble is suspected, may often be found extremely useful. Here is a means of supplying, at a moment’s notice, an extemporized illuminant of this kind. Take a well-cleaned spoon, and hold it against a candle flame, when you form an excellent mirror, which will permit you to concentrate the rays of light and produce at the back of the throat enough illumination for the making of a careful examination (Fig. 8).
A silver spoon, moreover, allows you to study the curious properties of curved mirrors. Holding the hollow part of the spoon before your face, notice that the head is at the bottom; turn the spoon round, and you have the bulging part a convex mirror, which will show an image, very long and narrow. If you approach this face in the spoon little by little, you will see the nose attain the most amusing proportions.
A DISAPPEARING COIN
If you look at an object which has been placed in water, owing to the phenomenon of refraction, the article appears in a different position from that in which it really is.
It is due to this phenomenon, therefore, that a stick, when half plunged into water, seems to be bent or broken.
A very interesting experiment based on this principle is the following:
Take a bowl full of water, and at the bottom place a coin. Next request one of your friends to lower his head until his eye, the edge of the bowl, and the near edge of the cent, appear to be in the same line.
As a matter of fact, it is not the coin itself that your friend can see, but only the image created by refraction.
Now, keeping your friend in the same position, inform him that you intend to make the coin disappear from his view.
To do this, remove some of the water from the bowl, which may be accomplished by means of a small syringe (Fig. 9).
FIG. 9. The disappearing coin.
Directly you lower the level of the water, your friend will no longer be able to see the image of the coin, which will be hidden by the side of the bowl. If, however, the extracted water be replaced, the image of the coin immediately reappears.
ELECTRIFIED PAPER
Very few people realize that paper can be electrified at a moment’s notice, no special apparatus for the purpose being required.
Take a piece of light paper, which should have been well dried, and rub it briskly with a clothes brush, silk handkerchief, or even the open hand.
After a little time the paper, becoming electrified, will adhere to your face, your hands, or your clothes, as easily as if it were attached by means of gum.
Nor is this property confined to thin paper. Thick paper, when dried, will act in the same manner. For instance, take a postcard, dry it, and rub it, and you will notice that, as is the case with sealingwax, glass, sulphur, &c., the card has the power of attracting light bodies, such as small pieces of cork.
The following interesting experiment may be carried out with an electrified postcard and a walking-stick.
Balance the walking-stick over the back of a chair, and announce that you can make the stick fall without touching it, without blowing it, or without interfering with the chair. This is easily possible by utilizing the electrified postcard.
FIG. 10. The electrified postcard.
First rub it on the sleeve of your coat. Now hold it near one end of the stick, and you will notice that the latter follows it as iron follows a magnet (Fig. 10), until the moment when the equilibrium being destroyed, the stick falls to the ground.
Of course the experiment may be varied by using any other suitable article in place of the stick, as for instance a fishing-rod.
ELECTRIFIED BALLOONS
From the last experiment it may have been gathered that if a piece of paper is dried and rubbed with a silk handkerchief or the dry hand it will adhere to the face, arms, or clothing.
It may not be so widely known, however, that if toy balloons be filled with air, and then stroked for a short time with a piece of fur, they will act in the same way as the electrified paper.
It is rather amusing to see these balloons, after being treated thus, placed against the wall or ceiling, where they will stick as if they were glued there.
Having entertained your friends in this manner, you may, by way of a little change, take two of these toy balloons, and, after having
electrified them, suspend them from the same point by means of two silken threads.
You will be surprised to find that the balloons now repel each other in the same manner as pith balls do (Fig. 11).
EXPLODING FLOUR
Flour will create an explosion!
FIG. 11. The electrified balloons.
Take a large handful of flour, and leave it for some time near the fire, in order that every trace of dampness may be expelled.
Whilst the flour is drying take a large tin box (a cracker tin will do admirably), and near the bottom make a small hole.
Through this hole pass the end of a piece of india-rubber tubing, and place the handful of dry flour in front of it.
At the other end of the box place a short piece of candle, and after lighting it, cover the box with the lid, taking care that it is not too firmly fixed.
If you now blow down the tube with your mouth, or better still, with a pair of bellows an explosion at once takes place, as a result of which the lid will be blown off (Fig. 12).
FIG. 12. Exploding flour.
If flour be not available the experiment may be performed with equal success by using fine dust, such as may be found on the backs of pictures, or collected from any elevated parts of the room.
THE APPARENTLY IMPOSSIBLE
Have you ever had tea on the top of a mountain? If so, you will agree that your cup of tea could by no means be termed excellent.
Now, why is it that a cup of tea made on a mountain-top is much inferior to one made at a lower level? If the fault lay in the tea, the defect could be easily remedied, but such is not the case, for it depends upon the fact that water on the top of a mountain boils at a lower temperature than water at the sea-level.
In order to make a good cup of tea, the water must boil at a temperature very near 100° C., and it is at this temperature that the water is generally boiled in your homes.
Why is it, then, that water boils at different temperatures at different altitudes? It is because, as the altitude is increased, so the atmospheric pressure becomes less.
At sea-level, atmospheric pressure is equal to about 15 lbs. to the square inch, but at the top of a mountain it is much less. The greater the atmospheric pressure the more heat is required before
the bubbles of vapor formed within the water can break at the surface.
After this explanation, perhaps the subjoined experiment will be attempted with additional interest.
Take a flask, to which should be fitted a good cork or india-rubber stopper, and in it boil some water, taking care of course to remove the stopper beforehand.
After some minutes the steam from the boiling water will have expelled all the air from the flask. Now remove the source of heat, at the same time quickly inserting the stopper.
If the flask is allowed to stand for a minute or two, the temperature of the water will fall considerably below 100° C.
Next inform your friends that, without applying any extra heat, you will cause the water in the flask to boil vigorously again. This seems to them impossible, especially when you tell them that you are going to do it by means of cold water. Quickly turn the glass upside down, and squeeze a sponge soaked in cold water on its upturned under-surface. Immediately the liquid inside will begin to boil, as if extra heat had been applied (Fig. 13).
FIG. 13. A curious boiling experiment.
But how are you to explain this apparently extraordinary phenomenon?
Well, directly the cold water comes in contact with the flask it causes the steam contained therein to condense, and, as no air can enter, thanks to the well-fitting cork, the pressure on the surface of the warm water is now considerably less than it was before.
Directly the pressure is lessened the vapor bubbles contained within the warm water are able to rise to the surface, and the water is seen to boil merrily.
Here is a very simple way of obtaining coal gas.
Procure an ordinary long clay tobacco pipe, the bowl of which should be filled with very small pieces of coal. Carefully cover the top
MAKING COAL GAS
with soft clay, and put the bowl in the fire, with the long stem protruding through the bars. Now watch this end of the pipe very closely and see what happens.
FIG. 14.—Simple gas-making.
Very soon you will notice a light-colored smoke issuing from the mouthpiece, but after a time this smoke disappears. But what happens if you hold a lighted match to the mouthpiece of the pipe? Immediately a bright yellow flame appears (Fig. 14).
The gas now burning is the same gas as is burnt in your house, although this latter, of course, is much purer.
If now you take the pipe from the fire, allow it to cool and then break it, you will be surprised to find that its contents have changed in appearance, for, in place of the coal, you will see what looks like a cinder. This is the coke. Thus you have manufactured gas from coal, at the same time producing coke.
EXPERIMENTS WITH CARBONIC ACID GAS
In a previous chapter, when describing how to make a miniature cannon, it was explained that the “gunpowder” with which the “shell” was fired is in reality carbonic acid gas.
It may not be amiss to show how to generate it, in order that you may discover for yourselves some of its properties.
There are several ways of obtaining carbonic acid gas, but most of these are of a complicated nature. The following, however, is an extremely simple method.
Take a 6-oz. or 8-oz. flask, and fit it with a cork with a hole, in which may be fitted a piece of glass tubing.
This tubing should be bent twice at right angles, as shown in Fig. 15, and the longer end should be allowed to dip into a large glass.
FIG. 15. A carbonic acid gas experiment.
Into the flask pour a little lemonade, soda water or ginger ale, and after replacing the cork or tube, heat the flask by means of a gasburner or spirit lamp.
You will notice that bubbles of gas are given off, and, as this gas is considerably heavier than air, it will, after being forced up the tube, displace the air in the glass, and gradually fill it. To test whether the glass is full, hold a match in the top. If the match is extinguished, the glass which is full may be removed. In this way several glasses can be filled, care being taken to cover each with a glass plate or cardboard disc to prevent diffusion.
From this experiment you will have discovered the three main properties of this gas (commonly known as carbon dioxide)—that it is colorless, is considerably heavier than air, and will not support combustion. Its high density affords another interesting experiment, which consists of pouring the gas from one glass to another (Fig. 16).
FIG. 16. Pouring carbon dioxide from one glass to another.
Take two glasses, one full of air and the other containing the carbonic acid gas, and into each plunge a lighted match. The match of course will burn in the glass containing air, whilst it will be immediately extinguished when it comes in contact with the carbon dioxide. You have thus clearly shown which glass contains air and which contains the gas. Now take the glass containing the gas and pour its contents into the other glass, in exactly the same way as you would pour in water. Again test with a lighted match and you will find that the gas has passed from one glass to another, thus proving that it is much heavier than air.
Next take two glasses, one containing air and the other carbonic acid gas, and, by means of a clay pipe, blow a soap bubble into each, carefully watching the different manners in which they behave. That dropped into the glass containing air will sink to the bottom, where, coming in contact with the glass, it will burst. The other bubble, however, as soon as it reaches the gas in the glass, rebounds owing to the high density of the carbon dioxide, but after a time, when it has settled down, it will float motionless on the surface (Fig. 17).
FIG. 17. Soap bubbles in A (air), and B, carbon dioxide.
Before you finish experimenting you should know how to detect the presence of carbon dioxide. Take a little lime water, which may be obtained from any druggist, and pour it into a glass containing
carbon dioxide. Shake the glass, and carefully observe the change which takes place. The lime water, which was previously colorless, has assumed a certain milkiness, and if allowed to stand the white powder causing this milkiness will settle at the bottom of the glass. This powder proves to be calcium carbonate, or chalk, which is always formed when lime water comes in contact with carbon dioxide, so that you have here a means of detecting the presence of carbon dioxide. Breathe into a little lime water and you will learn, from the milky appearance it at once assumes, that the air we exhale contains a certain quantity of this interesting gas.
CHAPTER XL PHOTO PASTIMES
CAMERA KNIGHTS’ EXPERIMENTS
IT has been presumed in commencing these notes that most would-be experimenters already possess a camera, or will at least shortly do so. Thus the greater number of experiments are such as would interest a camera fiend more deeply than the ordinary reader, although the latter might still derive much enjoyment from conducting them so far as the lack of a “dark box” will allow him. It will perhaps be as well to spend a paragraph at the outset in describing simply and noting a few peculiarities about the commonplace camera. Photography means drawing by the agency of light. Now light is reflected from an illuminated object in straight lines or rays, of which a proportion may be collected by a lens and thrown in points upon a surface behind. (See Fig. 1, A, illuminated object; B, lens; C, surface behind lens; D, rays of light thrown upon surface C.)
FIG. 1.—Rays of light collected by lens and thrown upon surface behind.
The front of a camera contains the lens, and is provided with a movable shutter, so that light may be only allowed to enter the dark box when a picture is to be taken on one of the sensitive plates inside. According to Fig. 2 which represents a camera in position to photograph the object A—the light is reflected in rays, which are collected in myriads of groups and cast pointed upon the surface of the sensitized plate B. Such ray groups—being parallel when they leave the object and pointed after passing the lens—are termed pencils of light, a most applicable name when they are employed in “sketching” a portrait on the photographic plate.
It will be seen that the action of the lens causes the base of the object to be registered upon the top of the plate, and vice versa i.e. the picture is taken upside down. Another noticeable feature about the magazine box camera, which does not, however, apply to the focussing camera with bellows, is that it may not be placed nearer than a certain distance (usually 10 feet or thereabouts) to the object photographed, or else the picture obtained will be blurred. The remembrance of this simple fact will save the loss of many plates to the tyro.
Finally a last note remains to be taken of the “stops.” These are really various sized holes in a metal screen, any one of which may be placed at will before the lens, and by the use of which the
FIG. 2. Camera in position to photograph object A.
sharpness or distinctness of the photograph may be improved. Thus a lens at full aperture will not give such a sharp picture as would be obtained if a small hole were used, but, as the amount of light permitted to pass in the latter case is much diminished, a longer exposure must be given. Consequently when a short-timed snapshot is being secured, the largest practicable aperture or stop should be employed, even though the sharpness of the picture be thereby to some extent sacrificed.
Having thus briefly reviewed the essential features of a camera, arrangements may be made for conducting our first experiment.
Experiment A.—A FIRESIDE PHOTO
Probably no souvenir can give greater pleasure to the amateur photographer, or prove more acceptable to his bosom chums, than their portrait, as a fireside group, lighted by the glow from a genial fire. Nor is this difficult of attainment.
First the figures should be grouped seated on chairs—and perhaps some standing behind, if many faces are to be included—in a quarter circle from one chimney-corner, whilst the camera may be securely placed some 9 or 10 feet away, about the position shown at X in Fig. 3.
FIG. 3. Relative positions of camera and sitters for a fireside photo.
Next some shade like a small fire-screen must be placed between the blaze and the camera, in order to protect the sensitized plate from the full glare of the firelight. Now of course the photograph is not actually secured by the coal flame illumination, which would not be bright enough to give proper exposure, so recourse is had to dropping some material into the fire which will burn rapidly with a bright white flame. Magnesium powder is generally used for this purpose.
Supposing the group to have been arranged and the camera firmly in position, the person (B, in Fig. 3) seated next the grate should hold a tablespoonful of saltpeter and also a square inch or so of sheet zinc. Then, all being so far ready, let the outside member of the group (marked A in Fig. 3) open the camera shutter and slip back to his seat, whilst the flashlight operator drops the saltpeter and zinc successively among the glowing coals. The flame of dazzling brilliancy which results records the sitters’ figures on the plate, so that directly it is over, the person (A) may again visit the camera and close the shutter. His movements will not be noticeable, since they are made before and after the flashlight.
The operation of development may be proceeded with at once and should go fairly easily, but flashlight exposures are difficult to estimate accurately, and therefore, although a square inch of zinc has sufficed for a small group with stop and an extra rapid plate, this amount may have to be increased if the group be large or if other conditions be changed.
One last hint as to behavior of the sitters. Let them sit as naturally and quietly as possible, but be advised to blink theireyes as much asthebrightlightpromptsthemrather than keep them staring wide open, when their faces must wear a most inane expression in the finished photo.
Experiments
B.—“P
HOTO-CHEMICAL”
Salts of silver form the basis of most modern photographic processes. Thus in order to perform chemical experiments of a
photographic nature, some solution of silver must be available, the nitrate salt being usually employed.
It is best procured at the druggist’s in solution or as crystals, in which latter case it must be dissolved for use in clean rain or distilled water. The solution need be only weak, but must be kept in a dark bottle screened from daylight. Chemical test-tubes, if they can be obtained, will be found best for the experiments.
FIG. 4. Silver solution and precipitate.
(1) Prepare a weak solution of table salt, and add it drop by drop to a little of the silver nitrate in a test tube (or wine-glass as a makeshift). A white sediment is precipitated, which, by shading part of the tube with a band of paper and exposing to daylight, may be shown to be sensitive to light, inasmuch as the unscreened part will rapidly turn purple. This precipitate consists of silver chloride, which, in combination with unaltered nitrate, forms the essential ingredient of printing paper. In Fig. 4, A is Solution; B, Precipitate; C, Band of Paper.
(2) Photographic plates are coated with bromide of silver, a yellow substance, which may be prepared similarly to the previous precipitate by adding potassium bromide solution (instead of table salt) to the nitrate of silver. Its appearance does not change rapidly under the influence of light, but if first exposed and then treated with a developing solution the yellow color very soon changes to black—finely divided metallic silver being, in fact, produced. Actually, light more readily alters the constitution of the bromide than that of the white chloride, but the former knows better how to preserve an outward appearance of composure.
(3) Suppose, now, another solution be made, this time of the fixing salt known familiarly to every camera knight as “Hypo.” When this is added to either the white chloride or yellow bromide precipitates above noticed, they gradually dissolve away, except such portions as have changed color under the influence of light.
Such action constitutes the process of fixing a photograph, whereby the sensitive silver compound is removed from those parts of the paper or plate which have more or less escaped the influence of light.
(4) This experiment is an aquatic performance in which one actor only—our old acquaintance Hypo—takes part. Provided proper care be taken in the preparatory stages, it will afford at the climax as excellent a spectacle as many another more complex.
FIG. 5. Preparing saturated solution.
FIG. 6. Grooved cork for “dripping” solutions.
A tumbler glass full of saturated solution has first to be prepared, and this is best done by tying about 1⁄2 lb. of Hypo in a piece of muslin, so that it may be held against the rim of the glass and allowed to hang in hot water after the manner of Fig. 5. When an appreciable quantity of the salt has dissolved, the liquid being but lukewarm, the muslin bag may be removed and the solution stirred gently. Then it must be stood somewhere firm, and allowed to remain absolutely undisturbed until cold. There should then be a glass full of clear liquid, and the phenomenon is at hand.
Let the smallest crystal of solid Hypo be dropped in this liquid, or let it but be disturbed, and behold! a wonderful transformation proceeds, until the glass interior becomes a shimmering mass of sparkling crystals. The reason of this curious behavior is not far to seek. Hypo, in common with most chemicals, dissolves to a greater extent in hot water than in cold, but is different, inasmuch as the excess of salt does not settle out as the solution becomes cold. Cold solution is therefore really over-saturated, and to such an extent that only an extra crystal or the least disturbance is sufficient to upset the delicate balance, upon which climax the great excess of Hypo soon settles out.
(5) This is another reaction in which Hypo takes part, but one other substance is required as well, viz. permanganate of potash. Condy’s fluid is equally suitable, and in either case the solution need only be weak—just a transparent deep pink color. The vessel containing this permanganate may be about half full. When Hypo solution is gradually dripped into this and the mixture stirred, the color is immediately dispelled, leaving the liquid clear as water.
Inasmuch as every photographer knows the necessity for washing his prints until all fixing salt is removed, this decoloring action may be fully employed in testing the washing water occasionally. When it no longer affects the tint of a pink permanganate solution he may rest assured that the deleterious Hypo—like some friends in being welcome so they stop not too long—has really departed. For the ready performance of this experiment it may be noted that any solution can most easily be “dropped in drips” from a bottle whose cork is cut grooved at both sides (Fig. 6).
Experiment C.—BLUE PRINT PAPER
Engineers’ drawings have for many years past been copied upon ferro-prussiate, or “blue print” paper. The original design being made in opaque ink upon tracing linen, a sheet of the sensitive paper is held against this in strong daylight until blue coloration has advanced everywhere except beneath the ink lines of the drawing.
These remain yellow, or rather white, when finished, as the excess of sensitive salt is removed by washing.
Since this last operation is in itself all-sufficient to insure permanency, the simplicity is unique. In fact, the impossibilty of securing other colors than blue has been the only factor to exclude this process from far wider use.
FIG. 7. Sensitizing blue-print paper.
The preparation of the sensitive surface presents no great difficulties, provided a drawing-paper of good quality be used. It should be cut into strips about 6 inches wide, which are passed one by one up and down (see Fig. 7) through a dish containing the following solution: 1 oz. ferri-cyanide of potash + 4 oz. water, added to 1 oz. ammoniocitrate of iron + 4 oz. water. (Note—4 oz. water = nearly 1⁄4 pint.) This must be done in very dull light—candle or paraffin oil by preference—and the wet paper pinned up to dry in a dark cupboard, hanging from the edge of a shelf or other projecting support. Then it may be cut into pieces of the required size and stored with a wrapping of tissue and brown paper in a handy box.
All manner of designs may be produced on this paper, such for example as fern leaves, lace, and embroidery. Actual sea-view photos or imitation moonlight views also look very well indeed. Another notion is to secure the copy of some picture printed in black on thin paper, which has been oiled and dried in order to render it translucent for quicker printing. The final washings should be thorough, and then the blue print will last its maker as long as the latter cares to keep it.
Experiment D.—TO SHOW THE CONSTITUENTS OF
WHITE LIGHT
Few physicists to-day doubt that light consists of waves set up in an all-pervading medium called ether; that, moreover, white light is composed of different tinted rays—to be seen reflected from the bevel edge of a looking-glass, or indeed from the more natural rainbow—which further are caused by the different lengths of waves whereby the colored lights are propagated.
Now we may produce these phenomena for ourselves by cutting a slit 11⁄2 inches long in a temporary window-shutter, or, more conveniently, in the end of a large wooden box (A, Fig. 8). Near this a glass prism, such as once adorned gas-pendants so profusely, must be supported (B, Fig. 8) on a block of wood, and at the opposite end of the box a sheet of paper pinned to the inside (C, Fig. 8). The arrangement is shown in the diagram.
Now notice, if you regard this screen from the open top—a large cloth covering head and box in order to keep out superfluous light— a band of color is depicted thereon, gradating gently like a rainbow from violet through blue and yellow to red. Thus the white light which entered through the slit has been separated into its component parts. So far, gorgeous enough! But for the photographer much greater interest is at hand, will he proceed as follows. Place the box so that bright sunshine enters through the slit, and after fastening a piece of blue print paper instead of the white on the box interior, allow this to print, at the same time excluding extraneous light by a dark cloth overspread. When this piece of paper has been washed and fixed, the colored band should have registered itself in various shades of blue, from which it will be noticeable that the purple and blue lights have darkened the paper most, whilst red and yellow hardly affect it at all. If ordinary printing paper, or still better, a photographic plate (in which latter case a considerably shorter exposure will suffice, and outside light must be rigorously excluded) be used, instead of the blue print paper, the result is still more striking.
FIG. 8.—The refraction of white light into its constituent colors.
From this experiment further is to be gathered the reason for developing plates by red light, which evidently does not affect the sensitive surface in any appreciable degree. But, on the other hand, special orthochromatic plates are made which, by dyeing, have been rendered sensitive to the yellow rays as well as to the blue, and if one of these be employed to “take” the colored band, technically called “spectrum,” a totally different gradation is obtained compared with that on an ordinary plate or on “blue print” paper.
Then again, suppose instead of sunlight, ordinary lamplight or incandescent gas be used as an illuminant, the gradation varies, whilst still another modification is to photograph the spectrum of a methylated spirit-flame in which common salt is being burnt. In this case the light is so yellow that an orthochromatic plate must be used. Another illuminant worth testing is magnesium ribbon, which also may be ignited in the spirit-flame.
Before saying a final adieu to these spectrum results, one last item remains for remark—last but not least. We say that the series of visible colors extended from violet through blue and yellow to red, and that darkness obtained at each end. Well! Mount a plate or piece of printing paper inside the box, so that half of it is well in the darkness beyond the bluish-violet bands, and expose long enough to secure a slight opacity in these parts (i.e.where the blue bands fell) when the plate is developed and fixed. The half of the plate which
was in darkness and therefore apparently received no exposure, nevertheless develops darker than the remainder, seeming to indicate that some light, although invisible to the human eye, had affected the sensitive silver compounds in the plate. This is actually the case. The rays of light which exert this wonderful influence are called “ultra-violet,” meaning beyond the violet, and their existence explains, amongst other matters, why photography of the heavens has revealed the presence of many thousands more stars than can ever be seen by man. Such stars emit only “ultra violet” light.
Experiment E.—ONE PERSON IN TWO PLACES—AND SPIRITUALISM
Pictures of a man decapitating himself, or of the reader’s sister turning the skipping-rope for another girl, who is herself, may justly be called mystifying. Not only may they almost deceive the operator himself, but will quite nonplus the uninitiated, to whom proofs may thus be presented of the most impossible happenings. Two methods are applicable to the production of such freak portraits, viz:
(1) To photograph the entire picture in two separate halves on the plate, moving the sitter from one position to another for each exposure.
(2) To employ a background as dark and dim as practicable, whilst well-lighting the sitter and furniture, and giving a separate exposure for each position of the model. The latter procedure is by far the simpler, and provided reasonably correct exposures are given, success should not be very elusive.
To take for a concrete example the portrait of a boy playing checkers with himself. Hang up a curtain of black or deep-red material in some dark recess of a room, and a few feet before it stand a small bamboo table with checker-board, &c., complete, at which the person to be photographed may be posed sitting. As mentioned above, all available light must be concentrated on the group, whilst if the model be wearing light clothes, the effect will be enhanced accordingly.
As to the camera, this may with greatest advantage be of the focussing type, or at any rate a box instrument fitted with magnifiers, so that by being placed near to the sitter the latter may be rendered large and sharp in the portrait whilst the background remains indistinct. This should be of such a size that its somber image well covers the whole plate. A suggested arrangement for the tableau is sketched in Fig. 9.
The first exposure may be made with the person seated at 1—the left-hand side of the table—he either resting one finger on a checker as if about to make his move, or adopting such other pose as his acting capabilities may suggest.
Primarily the time of exposure should be just sufficient for the light-clothed sitter, and therefore not enough for the table and background, which receive a second exposure. This should be made when the model has taken his chair to the opposite side of the table, and again assumed a position natural to the player, who anxiously watches his opponent’s play.
A. Table.
FIG. 9. One person in two places.
B. Black or red curtain as background.
C. Fireplace.
D. White sheet as reflector.
E. Camera.
1 and 2. Positions of sitter in first and second exposures.
All possible care must, of course, be taken to keep the table undisturbed during the model’s movements, and also to insure that no lighter object than the sitter himself has a place in either exposure just where he appears in the other. For example, a pile of books must not be photographed during the first exposure just behind or in front of the position which the model is to occupy during the second exposure; otherwise the vision of books through the person’s transparent chest, or a similar incongruous phenomenon, will result.
SPIRIT PHOTOGRAPHY
Spirit or ghost photography is but a modification of these methods. The chief element of success is to ignore the caution of the preceding paragraph, and render the ghost figure as transparent as possible. The first exposure should be an adequate one of the human model, who has twisted himself into an attitude of groveling terror compatible with the fright from which he is supposed to be suffering, whilst the background behind him must be dark and indistinct, if he is next to impersonate the spook. The latter’s surroundings, on the contrary, may be as detailed and well-lighted as convenient, because the white-robed figure is to appear transparent.
A sheet will be fit apparel for the “spirit,” and must be large enough to drape entirely the gliding form with outspread arms. The second exposure must be abnormally short, so as just to obtain a faint impression of the sheet and its folds. Finally, if the terror-stricken person can maintain his attitude of fear during the first exposure, and also for the photograph of the ghost, whose rôle
may be taken by some one else beneath a sheet, there is no necessity to have any part of the background unusually dark. Still, darkness is said to favor spooks, so the background is perhaps entirely a matter of choice.
With such dash toward the borders of the spiritual realm, this series of photo experiments must conclude. The most ardent camera fiend can scarcely denounce them as embracing too narrow a field when he considers that ghosts as well as mundane matters— psychical and physical alike—have been approached. Even if his finger-tips do not resemble ebony with silver nitrate, he may still rightly term his hobby the “Black Art.” And his friends! Well, if present at the researches, may their remarks be unheard. Doubtless they will ponder deeply, and conclude that the camera does sometimes lie.
Sun pictures of the earliest types had been no long time in existence before a rumor spread that photography could not lie. Critics and admirers of the new process rightly enough concluded that a knight of the camera must be constrained to narrow interpretations by his instruments as no artist is by his brushes. But this conclusion, held widely now as then, is only in part correct. The camera records the relative position of objects absolutely, but may on the other hand ruthlessly destroy all sense of perspective, or render globular images of rectilinear buildings. Nor are these the only peculiarities which, in themselves disadvantageous, may frequently be turned to account by the photographer.
Sensitive plates are seldom correctly exposed. They either suffer under- or over-exposure, and when there is a gross error the resulting picture either lacks detail and is blotchy, or else presents the light gradation of a London fog. But, as a set-off to these failings, it might be noted that moonlight pictures are obtainable by excessively short daylight exposures, which give only the outline of the objects, and a contrast between light and shade appropriate to night scenes, whilst photographs of flowers, portraits, and cloud studies may mostly receive full exposure with advantage, the
softness of lighting engendered lending additional charm to such subjects.
FIG. 10.—Slanting screen (C) with circular aperture to equalize exposures of sky (A) and foreground (B) in landscapes.
Landscapes commonly reveal over-exposure of the sky or inadequate exposure of the ground and objects, because the amounts of light emitted by these respective portions differ so much. To obviate this difficulty an early photograph worker devised, and indeed used, the arrangement of a circular aperture before the lens, slanting so that it might not admit such large parallels of light from the sky as from the ground portion. The device is more easily understood from the accompanying sketch (Fig. 10).
The portrait hunter should rejoice to realize that, by judicious procedure, persons of the coarsest complexion may be flattered in their likenesses. Not the least valuable dodge is to render freckles and red blotches invisible by the use of orthochromatic plates, and, if necessary, a yellow screen, which articles prevent the pink skin from securing any advantage over
