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for simplicity sake, that the force applied by the elastic remained the same during the whole motion ; but this is far from the case. If we take the diminishing tension of the elastic, we find ourselves involved in a problem which is difficult to work out accurately ; but this we may see distinctly—that the forces applied by the elastic in the cases supposed would have to be at the commencement con siderably more than three and eight ounces, and that the risk of shaking the camera would be correspondingly increased. The condemnation of the use of elastic which we apply to the shutter of the drop form—that is, the one with one moving part—must be understood not to apply to that which has two parts moving simultaneously in opposite directions. In this case the reaction of the one which would act on and move the camera is exactly counter acted by the reaction of the other. THE TRIMMING OF PRINTS. Mr. W. Thomson, of Aberdeen, sends us some details with regard to his experience in punching out carte-de-visite prints by means of a steel cutter, such as is employed in cutting out envelopes; the two principal advantages of this method being the rapidity with which a large number of prints may be cut out, and the uniformity of size which is ensured. Suitable dies or cutters can be obtained to order in London and most large towns at a moderate rate—we believe from 6d. to 9d. per linear inch of cutting edge—and, if carefully used, they will remain in good order for years. Mr. Thompson says:— I use a die, a block of lead, and a mallet; and the enclosed photograph will give you some idea of the various articles in use. For C.D.V. size, I cut a whole sheet of paper into cartes with one stroke of the mallet, this being a very great saving of time, and also makes very much superior work to the knife and cutting glass ; moreover, the corners are nicely rounded to suit the round-cornered card mounts. A A.—The die. B.—The moulded lead block or plate, 10 by K in. C.—Block of cast iron, which is not required if a good solid table is at hand to lay the lead on. D.—The mallet. F.—The cut paper as it falls out of the die. The round hole in the centre of the die, A, is to admit a pencil for pushing out the cut paper. One of more elaborate con struction could be made, with a spiral spring, for the same purpose. E.—Negative showing the register paper in position. Any number of these papers can be opt from waste albu- menized paper. It is scarcely necessary to say that the prints must be so piled up as to ensure the exact superposition of the corresponding parts of the various impressions; and Mr. Thomson’s method of working to a register paper attached to the negative is easy, and will be found very convenient; but we have found a slightly modified system rather more convenient in actual practice. Two small patches of black varnish (say, about one eighth of an inch in diameter) are painted on the negative, just beyond the limits of the portion required to be in cluded in the stamped out picture, one of these patches being, let us suppose, at the top, and the other at the bottom. In the centre of each black patch a small round hole is cleared out with a pointed tool, so that the main patch prints white, and the central spot black. The prints which are to be cut at one time—perhaps three or four dozen—are now impaled on a couple of pins, care being taken that all face in the same direction, and that the pins run exactly through the register dots. The circumstance of the paper expanding rather more in one direction than the other affects the register to a trifling extent, but not so much as to occasion any inconvenience. Instead of cutting on a leaden plate, many persons prefer to use a board or slab of lime-wood, which has been sawn transversely, so that the end of the grain shall be directed towards the cutting edge of the die. We strongly recommend those photographers who turn out considerable numbers of carte pictures to adopt the method of cutting them out with a die; but for cabinets, and larger photographs, the advantages of trimming by means of the die are not so considerable. NEW FOREIGN LENSES. The progress made in photographic chemistry finds its counterpart, apparently, in the realms of photographic optics. In this country the two leading firms of Dallmeyer and Ross and Co. have both of them novelties in store; and from Germany we hear that instruments of new con struction have of late made their appearance. Of these latter we propose to speak, for, since photographers abroad employ English lenses to a large extent, it is only fair that we, in this country, should say something about foreign optics in return. Most opticians have busied themselves in the construc tion of compound lens systems. Since the introduction of the excellent wide-angle single-combination landscape lens of Dallmeyer, in 1864, single lenses have undergone no alteration. Moritz Mittenzwey, of Zwickau, in Saxony, among others, has recently brought out a single lens of particular construction. This instrument is said to embrace a very large field, and is always in focus. For portraiture is said to work with an aperture of J of the focus ; while in the case of group photography, the aperture is | of the focus. Even with a very large opening, there is very little un sharpness, we are told; but until the instrument has been patented, and is properly put before the world, it would be unsafe to allude more fully to the wonderful qualities claimed for it. The well-known firm Franais, of Paris, has made some stir of late with its "nouvel objectiv rectilinear it foyer multiples.” The construction is aplanatic, and by interchange of the different lens pieces—we think neither Messrs. Ross and Co. nor Mr. Dallmeyer would recom mend such a course with any of their lenses—as many as nine different combinations may be produced of different focus and power. The most powerful combination of these is about equal to that of a rapid rectilinear; while other aplanatic combinations are suitable for large land scapes, and give such straight lines, we are told, that they may be employed for reproductions. For tourists the lens is therefore a universal instrument; only he must be an intelligent tourist, for otherwise, like the fox in the