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May 7, 1880.] THE PHOTOGRAPHIC NEWS. 217 Uhe Photographic Zcs, ay 7, 1880. PHOTOGRAPHY IN AND OUT OF THE STUDIO. Collodion as a Generator of Electricity—The Sensi tometer—The DrAPIOTE — The Royal Academy. Collodion as a Generator of Electricity.—In last week’s Notes we mentioned that Professor Borlinetto, of Padua, employed cardboard coated with collodion in the con struction of an electrophorus, and we also mentioned that the Warnerke film was even still more capable of electrical excitement. Our attention has been called to the fact that Professor Guthrie has some time since utilized the mixture of collodion and india-rubber for this purpose, and also given it a wider scope. As regards electricity, it is very remarkable that if you rub glass with the sheet of india- rubber and collodion, negative electricity is excited, where, ordinarily speaking, positive electricity is generated. One of the applications the Professor has given to this collodio- caoutchouc is the formation of miniature balloons for expe rimental purposes. An ordinary glass flask is first coated in side with collodion by rolling the liquid round and round i inside. When dried, a layer of india-rubber is given to the collodion in the same way, and then another layer of col lodion, and so on, till fouror five thicknesses of collodion are reached. When dried the film is easily detached by lilting it at the neck of the flask, and pouring between it and the glass a little acidulated water. The balloon then comes out perfectly well shaped, and ready to be filled with any gas which it may be desired to try, and the neck is well secured by waxed silk or any other suitable means. In experimental physics there seem to be many useful applica tions of this medium, and no doubt it will come into use. Oue use we have made of it is to tie down the stoppers of bottles; and here its pliability is of great service, as there is none of that disagreeableness in opening a stoppered bottle which has been tied down with ordinary bladder. Photographers have before now brought into prominence some properties of different materials whose value had not been previously recognised. What would the German army, for instance, have done without the gelatine films made insoluble by exposure to light in presence of bichro mate of potash ? Their everlasting sausages would have had a hard time of it. The Sensitometer.—At a recent meeting of the Photographic Club—whose proceedings, by-the-bye, are not reported, and rightly so—Mr. Warnerke brought forward an instrument or piece of apparatus which he calls the sensitometer. Its object is to compare the relative sensitiveness of plates, and it consists essentially of different thicknesses of gelatine impregnated by lampblack placed in little squares on a glass plate. It is a most ingenious adaptation of an old principle to a new purpose. On each of the spaces is printed a number corresponding with the thickness of the gelatine. The two plates are exposed simultaneously to gas or daylight behind a pair of the sensitometers for any suitable time, and on development the last readable number which appeals is taken as an index of sensitiveness. Thus, suppose 8 and 10 are the two numbers, the first plate would bo only, say, one-third of the rapidity of the latter. We are not sure whether a scale has been made, and the numbers given above are only what may be called examples of guesswork. This is an instrument which no employer of gelatine plates should bo without, and may be used as a photometer as well. For instance, in a studio a piece of sensitized paper may be exposed in a fixed place behind for a fixed time, say half an hour, and the number reached will be an indication of the exposure re quired ; ora dry plate might bo similarly exposed and deve loped, and the number read would answer the same purpose, always provided that the plates employed were of the same make. This, however, need not be a drawback, as any two batches of plates can be compared by the same instrument, as already indicated. Warnerke's photometer, or actinometer, whatever it may be called, which is dependent on phos ¬ phorescence, will, however, enable the photographer to be independent of this more elaborate arrangement. It would be a boon to the photographic world if Mr. Warnerke would enable it to procure this simple piece of apparatus. We might suggest that a standard scale and a standard light should be universally adopted to enable plate makers to at once compare the rapidity of their own plates with those of others by a simple reference to a table. The Diaphote.—Last week we adverted to this instru ment, whose object may be popularly said to photograph by electricity. Messrs. Ayrton and Perry, who might be called the Japanese twins of science, gave their idea of the matter, basing their hopes on the selenium experiments carried on by Professor Adams some two years back. The notion is a very natural one, and has been brought forward to our own knowledge at least three times, and how many more we should be sorry to say. France, that country of theoretical more than practical invention, was, we believe, the first country in the field, and the “ notions ” coming from there cover a very wide field indeed. In the Glol>e, too, the other night, we read that a Professor Minchin has developed photo- ' graphic action at a distance, by means of electricity ; so did Becquerel many years ago, and it is nothing new. Baines’s recording telegraph is really the same thing. We have no doubt that an accurate copy of a picture in gelatine could be copied on the same principle that the telephone is worked. The greater distance of a needle or pointer passing over the image from a metallic plate beneath it, at one end of a wire, would excite a less quantity of electricity at the other, and a consequent less decomposition by the current of some readily acted upon compound. This would give true gradation, and might be utilized, but will probably be more of a scientific curiosity than of any great practical utility. The ardent Amaranthus in New York or Calcutta will still have to wait awhile before Araminta can send her portrait by telegraph. 1 he Royal Academy.—The private view of the Royal Academy is over, and the public can now criticise for them selves. In our opinion the exhibition is more than ordinarily good, and the subjects more interestin-' than last year. There are many new names in the list of exhibitors, and some whose works have been accepted, without having failed in previous years to gain admittance. It has struck us, what a pity it is that some of the beautiful pictures which hang upon the walls cannot be popularised by means of photo graphy. For a few months a good picture can be seen by the public, and is then, so to speak, imprisoned in the mansion of some one who in all probability is a lover of art, rather than a lover of his fellow-creatures’ enjoyment, and to the large majority of those who may have lingered over its beauties the remembrance of it fades into a misty kind of affair in the brain. Now a photograph would recall vividly to mind the subject, and its special treatment by the artist, and in these days of bromide plates the repre sentation would be fairly accurate, since the yellows would not be represented entirely by a hideous black. A series of photographs published by some enterprising publisher would no doubt find a ready market amongst lovers of art, and it might be possible to induce the artists to allow such an undertaking to become a possibility. We believe we are right in saying that nearly every artist has a photo graph taken of his pictures for himself, but, unfortunately, we are equally aware that the persons who undertake this private work are often incapable of doing full justice to the pictorial effect, since they are frequently chosen more “on the cheap,” than for real knowledge of the " finesse ” of the work that is expected of them. The natural result is an abuse of photography by artists in general, though we could mention names on whom praise is lavished instead : but this is only the case when some well-known man has been selected for the post of photographer. Mr. Black burn’s Royal Academy Guide is now a recognised institution. How superior it would be if the etching were replaced by well-executed prints in woodburytype or collotype.