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404 THE PHOTOGRAPHIC NEWS. [August 20, 1880 The toning of collodion transfers and opal enlargements frequently gives trouble, and many will care to know that large producers of portraits of this kind—such as Messrs. Brown, Barnes, and Bell, of Liverpool, and M. Lafosse, of Manchester—do not tone at all. The former firm some times put a little gold in the fixing bath, but this is only on rare occasions. Experience in developing alone yields a good tone, in the opinion of these gentlemen. The Liverpool firm have a predilection for pyrogallic development in summer, and iron development in the winter. For opal work they like a very limpid collodion which contains plenty of cadmium. Messrs. Parry and Tucker have published their import ant paper on the application of the spectroscope and camera in the analysis of iron and steel, to which we have already referred in these columns. When a body is sub jected to the intense heat of the electric spark, it is, as we know, volatilised, and emits rays of certain colours— or, more correctly speaking, of certain wave lengths. These wave lengths are constant for the same body ; hence it follows that when two or more substances are volatilised together, the spectrum formed may be regarded as a sum of the wave lengths, and if these are thrown upon a sensitive plate, we have a photographed spectrum. Theoretically, say the authors, a well-focussed photo graphed spectrum of any iron or steel should be an unerr ing index to its composition ; and in practice, although this is not absolutely true, the lines in the photograph tell us more than we could otherwise divine. The ques tion whether two steels are of the same quality might be settled in half an hour by photographing the spectrum of each, side by side, on the same plate, supposing the two metals to be homogeneous. The value of photography in this branch of scientific research may be gathered from one of the concluding para graphs of the memoir : “ There is something so absolutely certain in a photographed spectrum that it is most desir able, if possible, to establish photography as the basis of all spectroscopic work.” Levitsky, the Court photographer at St. Petersburgh, employs electric lighting in a most systematic manner for portraiture. He has an electric lamp fitted in nearly every room of his house, and is thus enabled to employ any apart ment he pleases as a studio ; and so successful are his pic tures that they are not to be distinguished from those taken in daylight. But to appreciate the full importance of M. Levitsky’s arrangement, it must be borne in mind that during the winter months in St. Petersburgh there is sometimes not more than a couple of hours’ daylight during the whole twenty-four hours ; while, as everybody knows, the season and gay time of the Russian metropolis happens just at this period. In M. Levitsky’s case, therefore, the game must be worth the candle. Photographs by gaslight. The history of photography is not a long one, but it is beginning to repeat itself. In 1855 Dr. Lover exhibited to the Dublin Photographic Society—for Dublin had a society in those days—an appa ratus for taking photographs by gaslight, the main feature of which was the introduction of a stream of oxygen into the gas, the latter having first been charged with carbon. With the assistance of a reflector there was sufficient light, we are told, to take a photograph of an engraving in a “remarkably short period.” In the opinion of a painter who has had much to do with the treatment of photographic enlargements upon canvas, the only trustworthy method of producing the latter is by the dusting-on process. If you can manage to apply a film stable enough to take the painting, you are never sure that it will not peel off after the picture is finished and hung. “ The Mayor of Manchester has lost his head,” the people of Cottonopolis used to say because a fine painting of the civic head began to peel after it had been hung some months. The best plan, however, is not to apply photography to the canvas at all, but to employ a transparent print upon paper, and to trace the principal features on the canvas through this. While waiting for some photographic process for trans ferring photographs into printing blocks, a good many of the illustrations for scientific works are now drawn on the wood from negatives. The surgeon, microscopist, astro nomer, as the case may be, instead of furnishing the draughtsman or cutter with a rough hand-sketch, supplies him instead with a photograph taken by means of a camera, which frequently finds a place in library and labo ratory now-a-days. A North country photographer the other day told us, he was delighted at having taken a spell at gelatine plates in the studio. He practised the dry process for a full month, and it was most refreshing to come back once more to wet collodion plates, whatever their attendant troubles might be. After flashing drop shutters and instantaneous films, hot closets and fiery ruby, to get back to slow exposures and slow development, he assured us, was positively delight ful, and even the smell of collodion in the yellow-lighted dark room was grateful to the senses. Many of our readers must remember Paul Bedford. The ponderous comedian came up to town one day from Edinburgh in the “ Flying Scotchman ” ; the rattle, the vibration, the tearing speed of the train all the day through was too much for the old gentleman’s nerves, and he arrived on the platform at King’s Cross half deaf with the noise and bustle. He picked out the craziest four- wheeler he could find, horsed by an aged quadruped of feeble mien. “ Can you drive a mile an hour, my boy ? ’’ he asked the driver. The man of many capes vouched his ability to do so. “ Then for goodness sake let me get in.’ Paul Bedford used to say, he never enjoyed a ride so much ; at the same time, four-wheel cabs and four-wheel photo graphy are not agreeable under all circumstances.