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other end I provide an end which telescopes within the body, in which a dark slide, consisting of a frame with back and shutter, and having a plain glass fixed therein, which is pro vided so that either sensitive paper or glass can be used as required, and which at the same time registers a position for correctly focussing the plate by the use of a smaller piece of ground glass which is held against the clear glass in the dar slide until the proper focus has been obtained by the telesco J movement, after which the sensitive glass or paper is insert . in the place of the ground glass, in which position it will . j understood, it is exactly the same focus as the ground glass used for the purpose of focussing. The action of using my enlarging camera is as follows :— I insert the negative in the carrier with the film towards the lens. Draw the shutter, take out the back of the dark slide, and adjust the lens partition, and slide prt until the required focus is seen upon the glass in the dark slide. To move the lens partition I remove the cap from negative end, which then admits the hands, after which I focus accurately by placing the square of fine ground glass against the large piece of clear glass about midway between centre and edge in any direction. I then charge the slide with the sensitive paper or plate in the dark room with its face next the glass, replace the back, and see that the shutter is closed, after wards inserting the slide in the camera, and exposing accord ing to circumstances. My improvements, therefore, consist in the particular arrangement and construction of the various parts, as well as the use of the clear glass in the dark slide, the whole forming a compact, portable, and cheap enlarging camera, easy of focus, and capable of being worked in the light and with an ordinary lamp. 2,626. February Uth, 1890. “ Opalescent Glass.” CHARLES HUELSER, of Huelser and Co., 142, Fleet Street, London, Solicitors of Patents, (A communicatian from abroad by Joseph Kempner, of Berliner Strasse No. 60, Goerlitz, Germany, Merchant.) The object of this invention is a new process, derived from melting experiments, for producing opalescent glass. Said experiments have demonstrated that fluorides of alkalies alone do not produce opalescent glass—which fact is also estab lished by other tests (ride Dingier’s Polyteehnisches Journal, vol. 256, p. 361, 1885)—that even cryolite produces opales cent glass only if added in a large proportion ; that, however, silicofluorides of alkalies (silicofluoride of sodium or silico fluoride of potassium) or compounds thereof, when added in a relatively small quantity to a glass batch of any suitable composition, produce an intensely opalescent glass. The communicator, for instance, ascertained that when adding to three equal batches of the same composition respectively ten grammes of fluoride of sodium, cryolite, and silicofluoride of sodium, the first two mixtures resulted in a perfectly clear white glass, but the third mixture, containing silicofluoride of sodium, in a completely milky, opalescent glass. When making batches for opalescent glass in glass works, the proportion of silicofluoride of alkali to be incorporated will naturally depend on the nature of the substances con stituting the glass batch, on the temperature of the furnace, and on the degree of dullness desired to be produced. If, for instance, in an ordinary cryolite opalescent glass batch consisting of 30 units of cryolite, 46 units of carbonate of soda, 12 units of chalk, and 165 units of sand, the cryolite is replaced by 25 units of silicofluoride of sodium, and even tually 20 units of kaolin, a glass perfectly equal to cryolite opalescent glass is obtained ; the kaolin, however, is not abso lutely necessary, but any other aluminiferous mineral may be substituted therefor, as it merely serves to produce a glass similar to cryolite. Silicofluorides of alkalies may also be advantageously em ployed for enriching any opalescent glass batches. In the batch above referred to, for instance, 15 units of the cryolite con tained therein may be replaced by silicofluoride of alkalies. The batch, which would then be composed of 15 units of cryo lite, 46 units of carbonate of soda, 12 units of chalk, 165 units of sand, and 12} units of silicofluoride of sodium, results in an opalescent glass, which is at least as good as if only cryo lite had been employed. 9,715. June 23rd, 1890.—“ Photographic Cameras.” Alfred Julius Boult, 323, High Holborn, Middlesex. (A com munication from Hugo THUNTLER, 82, Potsdamerstrasse, Berlin, Manufacturer.) The object sought to be attained in devising this improved photographic camera is to combine the greatest possible economy with the advantages of a camera capable of being folded together in a compact form, so as to occupy a minimum of space when stored up for subsequent use or transport. To obtain this result the camera is preferably made solely of paper and cardboard. A bellows of cylindrical shape, made of pre ferably black paper impervious to light, is folded in the same manner as is usual in the manufacture of Japanese lanterns. Into one of the folds a cardboard disc is inserted and suitably fixed by means of paste, &c. In the centre of this disc is fitted an ordinary landscape lens. A few folds of the bellows remain free in front of the disc, and the front end of the bellow’s is pasted on to a square plate or sheet of cardboard in such a manner as to p-event the admission of light at the joint, and in the centre of which sheet of cardboard is provided a circular aperture for the admission of light. This wall fulfils the pur pose of a blind or shutter for the object glass. The opposite end of the bellows is also closed by means of a square sheet of cardboard, pasted or otherwise, attached thereto, so as to shut out all light at the joint. This sheet or plate is externally provided with a cardboard frame, the thickness of which should be somewhat in excess of the usual thickness of the glass plates used for emulsions, and to the outer surface of this frame another plate or sheet is secured. Both the cardboard sheets at the inside and outside of the before-mentioned frame are provided with cor responding central openings, preferably of circular shape, whose size is proportioned according to the space the image is to occupy upon tie negative plates. A square dry plate is in serted through the upper opening in the before-mentioned frame into a dark space provided for the purpose between the two last-mentioned sheets. The upper end of the outer sheet is extended so as to form a cover or lid, which carries on its inner side a piece corresponding to the portion which is want ing in the side of the frame, which side piece, when the said cover or lid is lifted, grasps the upper edge of the dry plate, so as to hold the latter in position. To prevent access of light to the dry plate when the camera is exposed to daylight, a narrow lid of a suitable fabric or strong paper is placed upon the front edges of the cardboard sheets, while a piece or cover suspended from the said narrow lid is placed against the rearmost sheet, which is made smaller on the sides and its lower edge than the frame and the sheet at the inner side of said frame. This deficiency is supplied by strips provided on the sides and the lower edge of the cover, which strips thus effectively shut out the light around the sheet. Two india-rubber bands attached to the rear of the cardboard sheet are passed over the cover at its top and bottom parts respectively, whereby the dry plate is securely locked in position. The bellows has a tendency to remain in its central com pressed position, so that when it is extended beyond this normal limit it exercises a spring action upon two stops diagonally fixed by means of flexible ties, preferably of fabric, each to one side of the front of the camera, and compresses the same between the sheets, front and back of the camera. These two stops consist of cardboard strips, and are of such length that, when it is desired to obtain sharply defined pho tographic impiessions, they extend the camera exactly to the required extent. When upon opening the lids, and at the back of the camera a ground glass plate is inserted in lieu of a dry plate, the photographic impression received by the camera may be in spected through the wide opening in the rearmost sheet. For the purpose of throwing light upon the emulsion plate, a lid or door is arranged in front of the opening in the front plate, and adapted to be raised and lowered as desired. To enable
