Chapter XXII: Ingenious Adaptations for the Lantern

BY W. J. GORDON.

I.--CHROMATROPES AND PAPER FIREWORKS.

From Mr. Chasemore’s article on revolving slides for the magic-lantern we borrow the following diagram, as showing very clearly the principle which such slides are constructed (Fig. 1).

Round the slide runs a wooden border half an inch wide and three-eighths of an inch thick. The right-hand part of the slide is wood, the left glass, and the moving part showing towards us is also of glass, and fits into a circular wooden ring that is kept in position as it turns by the two tiny buttons on each side of it. One of these buttons works on the frame, the other is fastened to a piece of wood glued on to the wooden part of the slide. Farther to the right is a small silk reel, into which a handle is fixed, and an endless band from the reel round the circle in the buttons completes the machinery. All this is simple enough, and as it has already been described need not be gone into in detail.

The question with us now is how to apply this contrivance to the working of a chromatrope. A chromatrope is a lantern slide consisting of two or more pieces so painted as to give the effect on the screen of a set piece of fireworks. It is the easiest of all slides to paint, as it is purely geometrical, and the colours used require no mixing, but can be put on at once as they are got from the shop. And, best of all, the effects produced are far and away more brilliant than anything else in lantern practice.

The essentials are a fixed slide of some bold design--star-shaped, circular, octagonal, or what not--and a moving shade that is of spiral pattern. The spiral pattern is the secret of the whole thing. Let the above be spun behind a star, so as to be only visible through its rays, and the star will seem to be alive. Turn it one way, the waves flow outwards; turn it the other, the waves flow inwards. The standing pattern must have a centre, and the spiral must be worked on the same centre. That done, all is well. Sometimes a double spiral is desirable, and then the pattern in Fig. 3 is adopted. By it the outer part of the pattern (B) will seem to flow in a different direction from the inner (A). Paint the spirals any colours you please, providing that they are bright, and you get the results. Let reverse spirals appear in your fixed pattern, and you improve the effect. Have two revolving rings worked by the same wheel, one over the other, and the whole device will glow with life and brilliancy.

To begin modestly, take some simple design, such as that of the fountain in Fig. 4. Paint it on your slide, and stop it out all round with asphaltum or any dense black. Then fix to it a simple spiral disk, such as that given in Fig. 2, and the instant the spiral spins the water will begin to flow.

In all designs remember that the fixed slide must be broken up with black and colour, so as not to show the whole of the spiral at once. The wave should, as it were, sweep over the windows. For front designs nothing is superior to a good knighthood star.

The colours for slide-painting can either be bought ready prepared, or ground down on plate glass and mixed by Canada balsam or mastic varnish. Should the balsam be too thick, use a little turpentine. The clearest colours are lampblack, burnt umber, burnt sienna, raw sienna, gamboge, Prussian blue, verdigris, and scarlet lake, and these are put on in the ordinary way. Before you begin clean the glass carefully with a little water and ammonia. Copy the design through the glass, and it would be as well not to forget that unless you can draw properly on paper you are not likely to do so on a lantern slide, where in the intense light and enlargement every mistake and shakiness of line is exaggerated for the benefit of the spectators. For those who cannot draw, figures of men and animals can be cut out with scissors and pasted on the slide, so as to give a shadow entertainment, as a change from the bought slides. Others can buy transparencies and stick them on for themselves, but the result will never equal hand-painting. One more caution before leaving hand-painting, and that is, do not be in a hurry, and give your slides at least a fortnight to dry.

If the spaces of the chromatrope are too narrow, or the design is worked too fast, you will only produce a fog, just as you do when you spin a toothed wheel. If, however, the teeth of the two wheels be fixed on the slant and the wheels turned in opposite directions, the teeth will be visible--upright if the teeth slant the way the wheel turns, slanting if they follow the course of the wheel. The principle holds good with the chromatrope; the spiral is but a toothed wheel.

The chromatrope was invented by Mr. W. Allen. He called it the pyreidotrope. It was improved, and soon became known as Chinese fireworks. From it the paper fireworks still popular in some circles were derived.

Paper fireworks are merely large chromatropes painted on oiled paper instead of on glass, and lighted by candles instead of a lantern. The wheels, and stars, and plumes, and pyramids are just the same as we have been describing, only much larger. The transparent portions are got by perforations. The machinery is the same, but of a rougher pattern, and the moving parts, instead of reels and bobbins, are barrel-hoops and butter-tubs. From what has been said above, their construction is sufficiently obvious, and we conclude with a design (Fig. 5) that may serve for either purpose.

II.--THE LANTERN AND THE KALEIDOSCOPE.

Have our readers ever tried to work these together? If not, let them do so, and they will be rather surprised at the results. Begin in a small way, and treat the screen as the broad end of the kaleidoscope. Arrange it at an angle to the audience. Against it place two mirrors at the desired angle, just as in the well-known instrument, and then damp the screen and throw the image on from behind, so that it will take the place of the usual coloured fragments.

Chromatropes can be made in this way by devising a double slide, and filling up the space between the two sides with stained splinters of glass, beads, etc.; and this contrivance put into the lantern, and its image thrown on to the screen between the mirrors, will be multiplied into the most brilliant geometrical fireworks, whose pattern can be varied as often as desired by simply shaking the glass slide, so as to rearrange the coloured odds and ends. If the slide is a mechanical chromatrope, of course so much the better, as instead of one image of it there are many. Modifications of this experiment will easily suggest themselves to an ingenious lad.

III.--THE LANTERN PRAXINOSCOPE.

Yet another praxinoscope, and a remarkable one. M. Reynaud is the inventor, and may well be proud of his ingenious combination. The sketch is so clear and complete that but little explanation is necessary. In the first place, there is a magic-lantern; in the drawing it is of the lampascope pattern, in which, by means of openings at top and bottom fitted with a sheath, an ordinary lamp can be used, if necessary, instead of the usual light, the chimney of the lamp being hidden by the top scabbard, and the beam that would illuminate the room being checked by the cap on the top of it. Any lantern can be altered so as to suit this arrangement, but the balance must be kept, and there must be no top-heaviness, so as to upset the lamp, and the under-sheath must be of the right length, so as to bring the centre of the flame opposite the centre of the lens. Any ordinary lantern with an ordinary lamp will, however, answer every purpose.

In the side of the lantern an aperture is cut, and around it is fixed a small triangular box containing a mirror set at an angle of forty-five degrees, and having a lens, in the base, of a very low power, or hardly any power at all. At the top of this side-box is fixed an adjustable lens of the same type as that in front of the lantern. In the lantern itself is placed a slide representing a landscape, an interior, etc., and the image of this is thrown on to the screen. At the back of the side-box is placed a praxinoscope of novel construction, and the images from it are thrown on to the sheet through the lens at its top, so that, as in a dissolving view, we have the picture seen by the assembly built up out of the slides.

The praxinoscope consists of a crown of mirrors sloping inwards, surrounded by a ring constructed to take a set of glass slides mounted in a strip by means of connecting links of silk or calico. The slides consist each of one of the figures alluded to in the last section, which form the series of instantaneous photographs that have revolutionised our ideas of the details of motion. They are, in fact, zoetropic pictures, each differing but slightly in attitude from the other, and each representing one of the changes assumed in a complete round of some definite movement.

The slides are slipped into the ring. The light from the lantern shining through the glass throws the images on to the praxinoscopic mirror, and thence it is reflected through the top lens on to the screen. The ring and crown are arranged at the angles given in the cut, and when the slides are revolved by means of the band and pulley shown below them, the different pictures as they pass the lens are reflected on to the background, and the figure appears in lifelike movement.

The lantern praxinoscope thus makes the zoetropic effects visible to a large assembly seated at their ease, and gives pictures of heroic size instead of the tiny proportions with which, when confined to the ordinary instrument, we are forced to be content. Many modifications of the arrangement will readily suggest themselves to our readers, and need not therefore be specially described.

1. Heyst Fishing-Boat from Belgium. 2. Native Fishing-boat from Aden. 3. Swedish Seal-Hunting Boat. 4. Type of Dutch Boat. 5. Fishing-Boat of Swatow. 6. Boat and Method of Fishing at Ningpo, China.]