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THE PHOTOGRAPHIC NEWS Vol. XXIX. No. 1409.—September 4, 1885. CONTENTS. PAGE A Few Remarks on Paper Negatives 561 Solid Electrolytes 561 Action of Light on Silver Chloride 562 How to Succeed in Taking Good Pictures on Gelatine Plates. By S. R. Bottone 562 Artistic Feeling in Photography. By A. H. Wall 563 An Amateur Afield with Camera—his Musings. By J. Gale... 561 Meteorology for Photographers. By J. Vincent Elsden, B.Sc. (Lond.), 566 Patent Intelligence 571 Photographic Experiences of a Native of the Far East. By S. K. Lawton, Jaffna, Ceylon 571 PAGE Notes 568 Reviews 571 Another Attempt to Photograph the Solar Corona Without an Eclipse. By Win. H. Pickering 572 Fancied Dangers of Ammonia Development 573 Theory and Practice of Photomicrography. By Maurice N. Miller, M.D 574 Correspondence 574 Proceedings of Societies 575 Talk in the Studio 575 Answers to Correspondents 576 Photographs Registered 576 A FEW REMARKS ON PAPER NEGATIVES. Now that paper negatives areagain engaging the attention of photographers at home and abroad, it might be well to point out one or two likely rocks upon which a novice may stumble. Our first consideration, were we about to prepare a flexible film of this kind, would have reference to the paper itself; and putting aside just now various methods of rendering the same transparent before coating, we should content ourselves with seeking a material possessing some degree of strength when wet, as well as fineness of texture and hardness, since these conditions lend considerable aid in the production of a good negative. This will very probably be provided for in a little while to our complete satisfaction by those who have undertaken the manufacture of negative films. Indeed, we have seen very perfect negatives made on several occasions at photographic societies’ meetings and elsewhere, upon papers emanating from commercial sources. Assuming that a reliable material can always be ob tained, and that the basis of the film is paper, it becomes a question whether printing should be conducted through the paper in its opaque condition, or made translucent by ordinary means. We do not think there is an enormous advantage apparent in using mediums which in course of time dry out, and of these castor oil alone, or dilute ether, with ether or turpentine, stands pre-eminent; neither is there any doubt about the messy condition of silver prints made from such negatives, unless the most scrupulous care has been exercised by the printer. The mixture some times used for rendering photographs transparent in the crystoleum process has certain advantages in this respect, since it does not so easily affect paper in contact therewith, and this is really a matter of great importance. It is com posed of white wax two ounces, solid paraffin two ounces, Canada balsam five ounces. These are melted together on a water bath, and the mixture must be applied warm, or by means of a heated iron plate, as in the old waxing pro cess. Those who do not like the trouble of waxing, can, in a great measure, supersede that process by the use of vaseline, applied cold, as recommended last week. Heat ing, however, in order to effect greater translucency, is liable to cause this substance to dry out in opaque patches ; moreover, it is somewhat greasy. Linseed oil is one of the best mediums that cau be used, but under ordinary conditions it takes too long to dry. Boiling improves it in this respect, but not sufficiently to be of practical value: still, if the method suggested by Mr. J. Sutton at the last meeting of the Loudon and Pro vincial Association be adopted, paper so treated will dry in three or four hours. His plan is to boil linseed oil of good quality until it has the consistency of treacle, During the period of boiling he applies a lighted paper to the top, and by this means burns off a good deal of the grease. Ordinary litharge (driers) and soap are then added. Mr. Sutton uses pieces of each about the size of a walnut with every pint of oil, after which the mixture is ready for use when required. It may be applied to any kind of paper when cold by means of a sponge, and yields when dry a very perfect result. The object of adding soap is to kill any grease that has not been burnt, and the proportion of litharge determines the time of drying. At the same meeting, it was a matter of discussion how best to secure sharp prints from paper negatives, and many ingenious ideas were forthcoming, but they have yet to be proved by practice. We know the difficulties experienced in obtaining perfect contact with glass negatives, and some of us remember instances of fuzziness and double images with Calotype negatives, notwithstanding that pressure frames were at least as well made then as now. Perhaps the manufacturers of negative papers will settle the point, as they appear to have done with exposing arrangements in the camera. In the meantime, we advise any one who finds it difficult to print large paper negatives, to put on as much pressure as the front glass will stand, and print a small negative of equal density for the purposes of examin ation and guide to depth of printing, thus rendering it unnecessary to open the frame during printing. SOLID ELECTROLYTES. Shelford Bidwell, writing in Nature, says :— “ In reference to Prof. S. P. Thompson’s letter dated August 17 {Nature, vol. xxxii. p. 366), may I be allowed to say that I too have observed the secondary currents which are produced by cells containing sulphides of silver and copper after being disconnected from a battery ? I mentioned the fact at the meeting of the Physical Society on J une 27, in a communication which will probably be printed in the Piulosiphical Magazine next month. In deed, the observation of these secondary currents preceded and led to the construction of the primary cells with solid electrolytes which I have recently described. “ I should be glad to know whether Prof. Thompson can explain the curious effect produced by passing a battery-current for a moment through a cell containing a mixture of sulphide of copper and sulphur between silver- electrodes. When the cell is first connected with the galvanometer the usual secondary- current appears, but in a few minutes, or even seconds, this current falls to zero, and is succeeded by a third, which is in the same direction as the battery current, and generally continues for some houjs.