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260 THE PHOTOGRAPHIC NEWS. LAPRIL 24, 1885. vogue, and many photographers acquired the knack of combining the images without the use of any instrument. This was accomplished in two different ways: one by squinting, so that the right hand picture was sufliciently dis placed in the image as perceived by the observer to the left, and the left-hand picture to the right, for the two to coin cide. This method, however, was not a proper one, but gave rather what is called a pseudoscopic effect. The other, and better plan, was to preserve the axes of the eyes parallel, as if looking at a distant object, whilst the focus was brought to bear at the distance at which the slide was actually held. The method of acquiring the ability to see stereo slides in this manner with a stereoscope is the following. Two pictures, which may either be identical, or as nearly so as the two halves of a stereoscopic picture, are mounted on separate card s, and cut so narro w as to allow them to be placed much nearer together than the two halves of a slide are generally mounted. These pictures are laid upon a plain surface where no disturbing bright object comes near them, and where they will be equally illuminated. A slip of blackened card is then placed in such a position as to resemble the partition in a stereoscope—that is to say, so that each eye sees only one picture. If the pictures are placed square to one another, and at an even height, and very near together, so that the same point in each is not more than an inch or an inch and a-half apart, the eyes will generally easily combine them into one, and they may then be gradually separated without their union being des troyed. When by practice they combine at a distance of from two and a-half to three inches, the ability to see a stereo slide stereoscopically without an instrument has been acquired. As stereo slides were commonly mounted at a distance (between some fixed point in each) greater than that which exists between the two eyes, it was necessary that the ability to use the axes of the eyes rather divergent than parallel, whilst preserving the focus for near objects, should be gained. I therefore considered that it should be practicable, where objects to be combined might be viewed from a distance of a few feet, that such objects should be capable of being combined in the observer’s brain when they are further apart from each other than three inches or so, which was their separation when viewed from a dis tance of a few inches only. Acting upon this idea, I placed two persons in a similar position, and succeeded in com bining their features into what is now called a composite portrait. This I did on several occasions, and perhaps Mr. Galton may be interested in repeating the experiment. As to a method of directly combining several images without necessarily photographing, there are two plans which I would suggest. One plan is to place a series of plates of flat polished glass (which should be as thin as possible, so as to reduce the effect of double reflection from the two surfaces to a minimum) at such an angle as each to reflect an image of one of the sub- Fig. 1. jects it is desired to compound. Let fig. 1 represent a stand with an eye-piece at the top, and glass plates, a, b, placed at the angles indicated. The cards, a', b', c’, will then be reflected in the glass plates, and if they are placed at such distances from the plates that the total distance— from the eye-piece to the plate, and plate to card—be the same, they will all be in the focus of the eye at the same time. One card may be laid on the base of the stand, and it will be seen through the glasses and unite with the others. Another plan, and one which will serve both for viewing combined images and for photographing them, is to have two or more lenses mounted as close together as possible. The lenses should not be large in proportion to their focal length. An illustration of two lenses will suffice to show the effect, whether that number, or three or four, or even more, are employed. When studying or copying photo graphs is in question, it is obvious that the pictures {a a, fig. 2) should be placed at just a distance that-their Fig. 2. images shall fall upon the same point, b, of the plate. A final exact adjustment, close to the operator’s hand, could be obtained by vertical and horizontal rack movements to the part of the camera front upon which one of the lenses is mounted. Several may be thus united simultaneously; but it would probably be convenient, in photographing a series, to keep the one which was used as the first always in place, opposite one lens, and arrange the others as they are placed in position opposite a second lens, so that the two images coincide as much as possible. In viewing the images of two individuals, the lenses might be slightly separated, if in the particular case the sitters would other wise be inconveniently close. More than two persons might be brought to the same place on the plate by the use of additional lenses, but the number’ would be more limited than in the case of com bining photographs, as the latter can be arranged verti cally as well as horizontally, an arrangement which would not be convenient with living subjects unless some had larger features than others, when they could stand behind at such a distance as to come to one size in the camera. REMARKS ON PHOTOGRAPHING PAINTINGS, AND ISOCHROMATIC PHOTOGRAPHY. BY W. M, ASHMAN. Photographing paintings is not by any means an easy oper ation, unless they are fnshly painted. Even then, certain colours in the original do not render up their true value to the photographer. There may have been two reasons at woik in the mind of the Hon. Treasurer of the Parent Society when he determined on reading his recent paper at Pall Mall. The first, we may assume, was to elucidate an interesting discussion which might enable experiments of recent date to be shown the light, and thus pave the way for the future enquiry suggested by the author of the paper ; or, as an authority upon the subject, Mr. Bird might have felt that British photographers awaited his opinion con cerning the action of the authorities who went out of their