The Boy's Own Book of Indoor Games and Recreations / A Popular Encyclopædia for Boys

by C. Stansfeld Hicks; John Nevil Maskelyne; Gordon Stables

Fig. 6.

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.

Fig. 7.

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.