Volltext Seite (XML)
JULY 9, 1880.] THE PHOTOGRAPHIC NEWS. 325 Uge | hot ographic Ycbs, July 9, 1880. PHOTOGRAPHY IN AND OUT OF THE STUDIO The Permanence of Coloured Photographs—A Small Hot-air Engine for Electrical Purposes—Instan taneous Photographs—Photographic Reproduciion. The Permanence of Coloured. Photographs.—The question of the alleged adulteration of artist’s colours introduced by Mr. Holman Hunt has not a little connection with photo graphy. If it be true—and there is little reason to doubt it —that a chemical reaction is set up between different colours when mixed together, how much more risk must there be when the colours are laid upon a chemical substratum, as chloride of silver, with perhaps an addition of a small quantity of hyposulphite ! It is an unfortunate truth that coloured photographs rapidly change, and it would seem, indeed, as if no colour when laid on a silver print was able to stand for any length of time. Carbon prints are doubt less much safer. This is a matter our print-sellers should look, to as to buy (say) one of Mr. Payne Jenning’s ex quisitely coloured landscapes, under the impression it is going to be a " thing of beauty and joy for ever,’’ and to find its tints gradually changing into an indescribable neutral smear, streaks making their appearance, and blotches following suit, is one of the most exasperating things under the sun. Of course, the sole fault does not lie with the manufacturer of colours ; some of the blame must be attached to the artist who makes an injudicious mixture. But to ensure a safe amalgamation the artist should have some knowledge of chemistry, and ought to know what his colours are composed of. It is by no means certain that if Mr. Hol man Hunt choso to test the question he could not bring the Adulteration Act to bear against the colourman who sells as Naples yellow something which is no more the Naples yellow I of the older artists than chalk and water can be called milk, j Now, if Mr. Hunt took this action and proved to be in the right, every tube of pigment would have to be described Something like the following ; “ Venetian Red, a mixture of”—well, whatever may be the ingredients. The artist would thus see at a glance the danger which would arise by the mingling together of certain chemicals, pre-supposing, of course, that he has gone through the proper curri culum of chemical study. We fear, however, this union of I science and art will never take place. Imagine Sir Joshua I Reynolds or Turner being deterred from the production of any tint they had set their hearts upon by the fear of its not proving permanent. A Small Hot Air Engine for Electrical Purposes.—That the electric light will be in general use in the studio is pretty certain. It is only a question of time; M. Jamin, as our French correspondent noted last week, has been very success ful in solving the great problem connected with the light and the divisibility of the electric current; and this accomplished, the next question is the best form of motive power to work the electric generator. M. Jamin uses a gas engine, and no doubt such an engine is very efficient. The smallest gas engine, however, that can be procured occupies some con siderablespace, while in many cases the noise of the successive explosions by which the motive force is produced is very objectionable. So far as mere description goes, a hot air engine called by the inventor “ The Tom Thumb Hot-air Engine” would seem to offer more advantages than the gas engine, both in si mplicity and size. The Scientific American, which contains a diagram of the apparatus, says that its success is based on employing a comparatively low tempera ture, 2508 to 300° Fah. producing a pressure of four to five pounds per square inch, and operating on a broad diaphragm piston of relatively short strokes. The piston is formed of two circular metallic discs having between them a flexible diaphragm composed of a layer of vulcanised gum-elastic sheet; over this, externally, a layer of canvas, which protects the gum, and permits it from yielding to pressure. The heater presents some novel features, the heating surface being greatly increased by numerous thin plates or ribs cast in connection with the bottom, and rising almost to the top nearly the whole length. The heat being applied to the bottom of the box, the lower edges of these ribs are virtually in the fire, and thus the whole are readily kept at a suitable temperature. At the bottom of the apparatus is another piston box similar to the first, but larger, and having its piston below, or a valve in it opening inwards. This is the air-pump, and it is connected with one end of the heater by a pipe which has an automatic valve at the lower end opening upwards ; as this piston descends it fills the box with air, which in ascending is forced into the heater, and the valve in the pipe permits its return. The other end of the heater is connected with the upper piston box or meter by a pipe always open, the two formingone chamber. By this series of valves a succession of hot and cold air is made to circulate through the apparatus, raising and depressing the piston, and so putting the machine in motion. The engine is difficult to describe in all its parts without the assistance of a diagram, but is in reality of extreme simplicity, and therefore could be constructed cheaply. An engine suitable to propel a sewing machine is about twenty-five inches high by thirteen wide, and heated by an oil or gas-stove. An engine forty-five inches high is a quarter horse-power, while the full horse power is six feet high by three feet wide. The inventor is a Mr. J. Jenkins, of Philadelphia. Instantaneous Photographs.—The Photographic Exhibition of October next should present a host of wonders in the way of instantaneous effects. With a gelatine process capable of producing a photograph in a hundredth part of a second (we quote from the last discussion of the Photo graphic Society), what may we not anticipate ! Breaking waves used to he considered the ultima thuleol instantaneous photography: they are now no longer as caviare to the multitude. Imitators of Mr. Gale’s famous “swallow” will be as plentiful as blackberries, and no doubt we shall have some adventurous photographer endeavouring to secure a representation of the flight of the eagle, or, possibly, a streak of lightning ! There is one class of subjects, how ever, which we are inclined to think is wholly a waste of time to take any trouble over as exemplifying the capabili ties of instantaneous photography. A picture of a bicycle in motion, for instance, which the photographer proudly exhibits as an extraordinary achievement, really conveys no idea of instantaneity, and tho more rapid the exposure, and the more perfect the picture, the less sense of motion is con veyed. “ Look how perfectly every spoke is defined 1" exclaims the delighted operator. Exactly, but he could say no more had he photographed the bicycle when stand ing quite still. The same with a steam engine. We may presume that the engine is going at the rate of twenty miles an hour, because we see the steam coming out of chimney, and because—the photographer tells us so. But what is there besides to indicate speed ? Turner’s famous picture of “ Rain, Steam, and Speed,” gives one a much better idea of a train in motion than any photograph could, and yet what is there discernible ? Nothing but the faintest possible indication of the outline of a steam engine —the wheels, in fact, being scarcely visible. Had Turner painted the spokes, what an absurdity he would have pro duced 1 Now, in the case of animals the matter is altogether different. The idea in the mind of a horse’s or a dog’s legs when in motion is distinct in itself, and cannot be con founded with anything else ; hence the triumphs of instan taneous photography would seem to lie in this direction. The possibility of success in photographing moving animals opens up, however, some curious speculations. Is it not possible that our artists, in drawing horses galloping and dogs running, have been all wrong ? The conventional idea of a horse’s legs in motion is one thing, their appear-