Chapter XXI: How to Make an Aphengescope, or Apparatus for Exhibiting

PHOTOGRAPHS, OPAQUE PICTURES, AND LIVING INSECTS IN THE MAGIC-LANTERN.

BY FRANK CHASEMORE.

In the last chapter there is an illustrated description of a magic-lantern for opaque slides, and as I have for some time used a contrivance on the same principle for use with an ordinary lantern, the few words I have here to say may not prove uninteresting. Like the opaque lantern, this modification of it is very inexpensive.

The interest of a magic-lantern is greatly increased by its being made to show photographs of friends or public men, and also pictures or engravings, Christmas cards, etc. This can be done by the following simple contrivance, which will cost but a few pence. Indeed, the one I use cost me only threepence, and is made out of a cigar-box; but a better and stronger one can be made for less than a shilling. It consists of a five-sided box, with top and bottom, as seen in Figs. 2, 3, and 6. In two of the sides are circular holes, and one side is left open about two-thirds of its length, which opening is closed by a door or shutter revolving on a pivot at the top and bottom, to carry the photograph. This shutter is fitted with four small clips on each side for the purpose of securing the card in its place.

Now for the construction. Get some thin board--deal is very good for the purpose; it is to be a quarter of an inch thick--cut two pieces out of it for the top and bottom, the shape shown in Fig. 1.

The dimensions of these pieces are as follows. The sides B and E four and a half inches long; the side A five and a quarter inches long; the other two sides are each to be three and three-quarter inches long. The angles where A joins B and E are each to be a right angle; so is the angle where C joins D. The two other angles are to be a hundred and thirty-five degrees each, as marked in Fig. 1. The sides of the box are to be eight inches long each, and are a little less in width than the edges of the top and bottom that correspond, so that when put together the outside of the box is flush with the top and bottom. The joints are to be glued together, and can be strengthened with pins driven in like small nails. The side E is not to be covered in all the way up, but only about two inches and a half from the bottom; but this depends upon the height that the nozzle of the lantern comes up this side when placed against it. Fig. 2 shows the opening left. When the glue is quite dry unscrew the brass focussing-tube from the lantern and place the box with the side C resting against the nozzle of the lantern, and mark round the nozzle on the side. Find the centre of this circle, and through it draw a line right across the side C, parallel to the top and bottom, and continue this line across the side B in the same way, as seen in Fig. 3. Find the centre of these two lines, and with these two centres mark a circle on each of these two sides, the one in the side B to be of a size to fit the brass focussing-tube, and the one in the side C to be about three inches in diameter, or large enough to allow the nozzle of the lantern to fit into it as far as it will go without coming between the picture and the lens, as seen in Fig. 4.

The remaining part to be made is the shutter to carry the photographs. This must be exactly the same size as the opening left in the side E, and is to be made out of the same quarter inch board. Let it be quite square at the sides and corners. The opening in the side E is to be equal in length to twice the distance of the centres of the holes in the sides B and C from the top edge of the sides where they join the top board. On each side of the shutter, in each corner, fasten a clip, as in Fig. 5. These clips can be made out of card or thin metal, cut in the shape shown, and fastened to the shutter with small screws or short pins. Mark the middle of the top and bottom edges of the shutter and place it in its place in the side E, and mark on the side the points where these marks come to. Take the shutter out again and bore a hole in the bottom edge of it about half an inch deep, and large enough for a stout pin to go into. In the lower part of the side E, and in the edge that the shutter will rest on, drive a stout pin in middle so as to form a pivot for the shutter, leaving out about a quarter of an inch, and cut off the head. Replace the shutter, fitting the pin into the hole bored for it, and drive a pin through the top board right into it, so as to form a second pivot. The shutter will revolve round these two pivots and expose the sides alternately to the lens. Fix two clips to the edge of the top board to keep the shutter in place while shut. Cover the whole of the box with unglazed black paper.

This simple little apparatus is all that is necessary to show any picture on the screen. To use it, first screw the tube carrying the focussing-tube into the hole cut for it in the side B, and push the nozzle of the lantern into the hole in the side C as far as it will go. Light the lantern and place the whole on the table so that the back of the lantern and the focussing-tube are directed to the screen, as seen in Fig. 6. Now place a photograph in the clips on one side of the shutter, and turn it round and put one in the clips on the other side. The photograph inside will be strongly illuminated by the light from the lantern, and an enlarged image of it will be projected by the lens on to the screen. The photographs placed on the shutter of the aphengescope must be, of course, upside down, as the lens will have the effect of inverting the pictures.

A strong light is required for this apparatus. The ordinary oil lamp will not show a bright picture at a distance of more than two or three feet. The ‘Triplexicon’ lamp, a lamp having three parallel wicks, burning paraffin oil, will give a good picture. But the best results are obtained from the oxycalcium and oxyhydrogen burners. These will distinctly show a large and brilliant picture, at a great distance from the lamp.

With this instrument, a watch placed on the shutter will show an enlarged image of itself, and the motion of the minute hand will be very distinctly seen. Anything that will go on the shutter will be shown on the screen. This adds greatly to the available articles to be used as slides.

Some of the most interesting slides are made by mounting entomological and botanical specimens on white cards, and putting the cards in the clips on the shutter, when enlarged images of the butterflies, moths, or beetles, etc., will be seen on the screen in all the glory of their natural colouring.

But the most interesting of all is the exhibition of living insects. This can be done in the following manner. Take out the shutter and lay it on the table: get a watch-glass, about two inches diameter, and deeply domed. Place this glass on the middle of the shutter, and with a lead pencil mark all round the glass. Remove the glass, and with a sharp knife cut into the wood of the shutter all round the pencil mark, cutting about one-eighth of an inch deep. Cut out all the wood inside this mark so as to form a hollow or well about two inches diameter and one-eighth of an inch deep, as Fig. 7. Cut the bottom of the well quite smooth, and line it with white paper.

Now get a piece of thin glass about the size of a photograph card, and thin enough to go under the clips on the shutter. Your shutter is now ready for the specimens. Replace the shutter and put a fly or other small insect into the well, and cover it with the flat glass, fastening it with the clips. Now turn on the light in the lantern, and focus the lens, and an enlarged image of the fly will be seen on the screen crawling about in a natural manner. For larger insects, such as a cockroach, wasp, etc., you must use the watch-glass to cover them instead of the flat glass. This can be fixed in its place by being pushed into the hollow or well, when the sides or walls will hold it. The two glasses are required for the reason that the insects ought not to have more room than will allow them to crawl about on the paper, as they would sometimes get on the glass, when they would be out of focus of the lens. But the glass must not be so close to them as to pinch them. You will have to keep your living specimens in boxes, with air-holes so as to have them ready for the exhibition, and will also require a small pair of forceps to handle them by, being very careful not to injure them.

On page 247 I have told you how you can make a light and portable frame for the screen, at a small cost. Lads who have experimented in chemistry ought to be able to make the oxygen gas for the oxycalcium light.

This instrument, as here described, was intended for use only with the tin lanterns as sold in the shops, which all have tapering nozzles. It can, however, be used with the lantern described in my former article, but the stage of that lantern would require to be modified in the manner shown in Fig. 8.

Unsolder the large nozzle-tube from the front of the stage, and in its place solder on a band-ring of stout tin. This band is to be one and a quarter inch deep, and the diameter just enough to allow of the back end of the nozzle-tube fitting in it very tightly when the lantern is used in the ordinary way. The small turned-out rim of the nozzle-tube must be carefully cut off for this purpose. The aphengescope itself must have a small tin tube fastened in the small hole in the front of it, for the focussing-tube of the lantern to slide in; and the large hole must be cut large enough for the tin band on the front of the stage of the lantern to fit into it. This arrangement will allow of the light in the lantern being brought closer to the picture than can be done with the ordinary lanterns, and will, of course, illuminate it more strongly.

A very good lamp, with high illuminating power, to be used in any lantern, especially with this instrument, can be bought at the paraffin-lamp shops for a small sum. The tin duplex lamp, burning crystal oil, is the best. I should recommend any of my readers who have made, or are about to make, the lantern I have described, to get one of these, instead of making the lamp described with it, as it will give nearly twice the light. An arrangement will of course have to be made at the back for the reflector. If a lamp cannot be got that is low enough for the lantern, you can make the body of it yourself. You can generally get, at these shops, damaged lamps at a small cost. Get one that is damaged only in the body. Unscrew the brass-work, as though you were about to fill it, and put it on one side. Unsolder the brass screw-socket from the reservoir. Now make a square tin box for the new reservoir, covering in the top. The box is to be an inch and a quarter deep, and as large as the lantern will allow. In the top cut a hole to solder the brass screw-socket into. Then screw in the brass wick-carrier and make the clip for the reflector.

If a pair of lanterns are used the light will be proportionately stronger, and a strong light is an important thing with this instrument.

Fig. 9 gives the plan of the top and bottom boards of the instrument for use with a pair of lanterns, and requires no further description.