Volltext Seite (XML)
APRIL 17, 1885.J THE PHOTOGRAPHIC NEWS. 253 that in working the process we are obtaining results which, according to present experience, will be as perfect one hundred years hence as now, is not the least encouraging feature in the printing manipulations of this beautiful process. As regards the chemistry of platinotype, the subject is a somewhat complex one. The image, as the name implies, is formed of chloride of platinum reduced to the metallic state. In sensitizing, the paper is brushed over by a mixture of chloride of platinum and sesqnioxalate of iron, or, as it is more generally called, ferric-oxalate, this ferric-oxalate having the peculiar property of changing, by exposure to light, into ferrous- oxalate, and as ferrous-oxalate in combination with potassic oxa late (or the neutral oxalate of potash used in developing the prints) is a powerful reducer of chloride of platinum to the metallic state, it follows that, on the application of the plain hot solution of oxalate of potash, a combination is formed in the paper itself, which immediately develops the image by reducing the platinum to the metallic state. It will thus be seen that the faint impression which is distinctly visible before development is really formed by the darkening of the ferric-oxalate, used in combina tion with the platinum, by the action oflight converting it into ferrous-oxalate, and that hitherto the chloride of platinum has taken no part whatever in forming the image ; and further, that it is only when the hot solution of potassic oxalate is applied to the surface of the print, that the union of the two salts takes place and forms a reducing agent on the platinum, varying in intensity precisely in proportion to the different strengths of light passing through the negative, and representing the light and shade or gradation of tone in the picture. It may be that the commercial paper supplied by the Platino- typo Company is prepared in some way different from the above description—no doubt the large experience they have had in the working details of the process may have suggested many altera tions and improvements—but, broadly speaking, the principles will be much the same. Oorrespondence. A NEW DANGER. Silt,—The following will, I think, surprise your readers, and, at the same time, put them on their guard. About a fortnight since, 1 received an application (addressed to 49, King William Street, E.U.) from a party in Northampton, wishing to become a canvasser, and naming someone as recommending him. As I do no club work, and employ no canvassers, I thought there must be some mistake; but, about a week later, another applica tion came from another person residing in Northampton, on the same business, and my suspicions were aroused. Soon after this letter camo a gentleman from North ampton, to enquire if I employed canvassers in North ampton, explaining that his niece had paid some 8s. as deposit on a photograph. I immediately put myself in telegraphic communication with the victim, and this resulted in my making tracks for Northampton. My first visit was to the police. The sergeant received me civilly, telling me that the party spoken about by the victim had recently been released from prison, having been convicted for embezzlement, and that he was powerless to act, as his superior was absent. I made my way to an address of one of the candidates, who explained to me that he had been induced to subscribe some 20s. on account of two photographs, believing that they were to be done at my address, and while I was talk ing to this gentleman, who should pass the door but the canvasser in question. He was called in, and I taxed him with obtaining money under false pretences. He denied this, and when I asked him to accompany me to the police station, he refused ; but, by dint of a little gentle persuasion, I got him there. The inspector had not returned, so the sergeant and I went in quest of him. On our getting back to the office, we found he had returned. I was met with a rather indifferent remark, “that it was no business of theirs.” “ What,” I said, “not when a man is obtaining money under false pretences all over the town?” He advised me to take out a warrant, and that I could get one at the Town Hall at three o’clock—an hour and a-half to wait! I thought it better to pvt the matter in the hands of a solicitor, who will place the facts before the magistrate with the view of a police prosecution. I was almost forgetting to say that the explanation given about my address being on the card was, that the printer I had put it on without his (the canvasser’s) knowledge or permission.—Yours, &c., A. L. Henderson. 49, King William Street, E.C., April 11th. THE PRESERVATION OF MEMORIALS. Dear Sir,—In reference to your note on the “Preserva tion of Memorials,” in last week’s News, allow me to state that two photographs were deposited in the cavity of the foundation stone of St. Catheiine’s Church, Pontypridd, some twenty years ago. The photographs—which repre sented the exterior and interior of the old room in which church services had been held—I prepared as follows :— Made reduced collodion transparencies, which 1 cemented with Canadian balsam in contact with opal glass. I see no reason to doubt the absolute permanence of the pic tures, especially as they were sealed in a glass jar with the usual papers, coins, &c. ; and I venture to think that if ever that jar is opened, those little photographs will be considered the most valuable and interesting of its con tents.—Yours truly, Thos. Forrest. Pontypridd, April 11 th. [Now that photographs in vitrified enamel may be so readily made, they should certainly be used in preference to any other kind of photograph.— ED. P.N.] INTERNATIONAL LANTERN SLIDE EXCHANGE. Sir,— Sou will be interested in knowing that the Lan tern blide Exchange that I started in the autumn has been carried to completion, and that it has now ceased for the season. All the members have seen the slides con tributed by others, and the only mishap has been the breakage of eight of the slides in my own set. On the whole, the matter has gone off in the most satisfactory manner, and has bad the effect intended of giving each member the use of a large number of slides during the winter. Next winter matters will probably be managed in a slightly different manner, and instead of an " Ever- Circulation ” of slides weekly, a list of members, with the slides they have, will le supplied, so that those in the Club can make direct borrowings and lendings. My chief object in addressing you now is to call for members willing to take part in an “ International ” Ex change which I propose to arrange, in conjunction with Mr. Dresser and with Mr. Beach, the Pre sident of the Society of Amateur Photographers of New York. The object of the Exchange will be to pl ice in the hands of members in England a number of lantern slides taken in different parts of the United States and other parts of America this year These slides will be so made up as to be readily taken apart, so that members may take copies of those they may take a fancy to by contract. This can be done by binding the two glasses together by thin metal strips. The general conditions would be that each member should contribute ten approved slides either quarter-plate size, or the ordinary three-and-a-quarter square, and pay a season’s subscription of 5s. to pay costs of working the Exchange; the ten slides to be sent to me by the first week in September next, with a description of the subject, which must be some view of geneial interest, either in England or the Continent. Suitable metal strips will be supplied to each member to bind his slides with. As soon as all are col lected together, they will be sent in bulk to Mr. Beach, of New York, and will remain the property of the American
