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Juty 24, 1868.] THE PHOTOGRAPHIC NEWS. 351 and had began to expose his plate, when a high priest or ecclesiastic dignitary of some kind appeared on the scene, and made most unmistakable signs to the effect that he must leave the spot immediately. As the exposure had just commenced, the gallant Serjeant attempted to expostulate with him, in order to gain a few moments until the picture was completed ; but, unfortunately, as the period required was somewhat long, and the Abyssinian divine was becoming very energetic, both in his language and action, the valiant photographer deemed it prudent to beat a rapid retreat, in the performance of which strategic movement he unfortu nately lost his plates. A Captain Pottinger, an officer accompanying the expedi tion, made good use of a camera during the expedition, but his results with dry plates were not, we believe, very suc cessful. He was also unfortunate in not having his appa ratus at the front during the taking of Magdala, and was therefore, like the Engineers, unable to secure any view of the battle. We have had an opportunity of inspecting the apparatus and necessaries since their return to England, and the perfect manner in which they were selected, fitted, and arranged for transport reflects great credit upon Captain Stotherd, E.E., and Lieut. Harrison, R.E., under whose care and supervision the staff was organized and equipped. It must be some satisfaction to Serjeant Harrold and his companions to know that, in performing a difficult duty, they have been instru mental in securing of the Abyssinian Expedition many valuable mementos, some of which it would be impossible to replace. PHOTOGRAPHY IN GERMANY. BY DR. H. VOGEL. The Gordon Gum Dry Process.—With the greatest interest I have read your communications on the Gordon gum dry process, and I have repeated the experiments with it with the best results. I have made some trials for determining the relative sensitiveness of the gum process and the ordin ary wet process, and I found necessary thirty seconds for a picture on a dry plate, under conditions which required fifteen seconds for a wet plate, using the same collodion and the same baths. 1 have tried collodions with iodide and bromide of cadmium—the first sample, 1 part of bromide to 2 parts of iodide ; the other, 1 part of bromide to 1 part of iodide—but I did not find much difference in sensi tiveness. The Ilarnecker Dry Process.—Here, in Germany, a new dry process excites much attention—a dry process, indeed, which, from what I have seen, I believe is the simplest known. M. Ilarnecker, a very clever photographer and chemist, sells a dry-plate collodion. With this collodion one coats a plate and sensitizes it in the following bath :— Silver ... 15 grains Water ... ... ... ... 135 „ Nitric acid 2 minims Wash the plate as in Mr. Gordon’s gum process, dry it, and the plate is, without any preservative, ready for use. The plate is nearly as sensitive as a wet plate. I gave with success twenty-five seconds to a Ilarnecker plate, and twenty seconds for a wet plate, for a picture of the same details and intensity. The Harnecker plate is, after expo sure, put in distilled water, five minutes afterwards dipped in the silver bath above mentioned until the plate is evenly coated with it, and is then developed with the following developer:— Sulphate of iron ... ... ... 1 grain* Glacial acetic acid 3 grains Water 220 „ Alcohol 4 to 5 „ * An iron developer of 2 grains to the ounce seems unusually weak ; but «is so stated in Dr. Vogel's copy.—Ed. The picture comes as rapidly as a wet plate, and is strengthened in the pyro and silver in the ordinary manner. I do not know the composition of Harnecker’s collodion, but I believe it contains a resin ; but it is very curious that the bath does not fog after the preparation of the dry plates as it does with the old sensitive dry plates of Mr. England and others. But, in general, I must confess, that the results of the Harnecker process are excellent. Perhaps you have already heard of the Mausoleum in Charlottenburg, from our Queen Louise. It is a very dark room, with the celebrated statues of the queen, from the late cculptor Ranch. It was not possible before to make any other photographs of this dark interior except stereo pictures, with very actinic lenses, and these stereos only show a little part of this interior. Recently, Mr. Stiehns had made a large picture of this interior with Dallmeyer’s triplet and Harnecker dry plates, in a time of exposure of two hours, and this picture is excellent, and was very much admired in the Photographic Society. I think the Harnecker collodion will become very import ant for taking plates in long exposures. Photographic Seals.—A curious novelty has recently been published here by M. Sturmhoefel, in Freiberg. If you send your card picture and two thalers (six shillings) to M. Sturmhoefel you receive from him a seal with your portrait in relief. M. Sturmhoefel does not state the manner of making such a relief, but it is easy to guess:—Take a transparent positive on glass (perhaps one of your collodio- chloride pictures), print it on Swan’s bichromate gelatine tissue, and soak the latter in cold water; then you will re ceive an excellent inverse relief (the lights hollow, the blacks relief). Make from this a copy in plaster, and from this a mould in metal, and you have the photographic seal. The German Solar Eclipse Expedition.—In a few days I shall go with my friends, Dr. Zencker and Dr. Fritzjene, to Aden, in Arabia, for taking the solar eclipse; and per haps it may interest your readers to hear somewhat of our preparations. We are ordered to take (1) prints of the total eclipse (which in Aden continues three minutes) directly with a large single lens of Mr. Steinheil, which is corrected for optical and chemical focus, and which gives a sun picture of 5-6 inch in diameter ; (2) enlarged prints of the sun after and before the total eclipse at a diameter of 3} inches ; for making this wo have a large refractor, with an excellent clockwork, like the refractor made by Mr. Dall- meyer for the Wilna Observatory, and described in the Photographic News some years ago. We have selected Aden as our point of view, because to nearly all other localities where the eclipse is visible astronomical photo graphers will be sent from other nations, in Siam the Frenchman, in Persia your countrymen, &c. In this manner a photographic series of the different phases of the eclipse will be secured. Mr. Warren de la Rue has already described especially the manner for taking photographs of the sun, the moon and in a like manner we think to work. I fear that we are not so well equipped as your English expedition was, as we have only a single apparatus. It would be better to have two or three, for making more pic tures in the same time. We have tried our refractor (heliograph) here on the Royal Observatory, in taking the moon in a like position as the sun will have in Aden at the time of eclipse. The time of the eclipse in Aden is nearly six o’clock in the morning, and the sun will be at that time so low that I fear its actinic power will be very slight. We have taken the moon in a like low position in a bright weather with five seconds’ exposure, and have received a well exposed picture in one second time another day, and have necessary twenty seconds for well exposed images. Now Mr. Warren de la Rue states that the prominences of the sun during the totality are about three times as bright as the moon, and therefore we hope to receive in the time of totality (three minutes in Aden) at least three well exposed pictures of the
