eye one of the two binocular images. He afterwards constructed a refracting telescope, composed of two prisms of about 8° each, placed between the eye and one picture, and refracting the two images on one intermediate space, where they coalesced. Sir David Brewster recommended a stereoscope somewhat similar, but, instead of two common prisms, supplied with two semi-lenses, acting at the same time as refracting prisms, and as magnifying glasses, by which the pictures could be considerably enlarged. This instrument was so constructed that all direct reflection was avoided, which is an indispensable arrangement for the inspection of Daguerreotype surfaces; and this contrivance, and the convenient shape of the instrument, has been partly the cause of its great popularity and usefulness. This instrument was called by Sir David Brewster the lenticular stereoscope. Photography alone can produce two images perfectly identical to the two images on the two retinæ ; and if we can place them so that the right perspective is seen only by the right eye, and the left perspective only by the left eye, both in the line of direct vision, we have on each retina the same representation we had from looking at the natural objects. This is precisely the effect of the stereoscope; therefore, in the stereoscope we have the same sensation of solidity and distance as we have with two eyes. When we look at a solid object, such as a cube or a statue, it is obvious that the right eye sees some parts of the solid which the left eye cannot see, and vice versa. In looking with two eyes, the objects appear solid and separated from each other, because we are unconsciously taught to judge that what is seen by one eye, and not by the other, must be on a receding part of the solid, and hence the idea of solidity in our mind. When we direct our vision from an object upon an object nearer or more distant, we are obliged to shift the two retinæ in order to cause their axis to correspond with the new angle of vision, and to obtain a single vision. This is done with wonderful rapidity, and we are unconscious of the exertion. This phenomenon is beautifully illustrated by two photographic pictures on glass, intended for the stereoscope. M. Claudet, in a

lecture at the Society of Arts, showed that these two binocular images were not exactly similar-that each had a different perspective projection. He placed one against the other, and being able to slide them in a grooved frame, there was only one plane of the perspective in each picture which by the superposition could produce a single image; the objects on planes more distant or nearer were distinctly seen double; when the objects on the foreground plane were coinciding, all the objects behind were more and more separated, according to the distance; when the objects of the middle plane were coinciding, all the other objects before or behind were separated; and when the more distant objects were coinciding, all the others before were more and more separated as they were nearer and nearer. Therefore, in observing the two binocular pictures in the stereoscope, the eyes are obliged to alter their convergence in a certain degree for each distance, and it is to that exertion, and to the duplicity of the images, and their degree of separation both ways, that the mind has the sensation of relief and distance of all the objects represented in the stereoscopic pictures, and the process is exactly the same when looking in the stereoscope on the two binocular pictures, or when looking naturally at the real objects. If the two perspective projections of the Daguerreotype images are taken at a greater angle than they are with the eyes for the same apparent size, the optical axes have to alter their convergence in a greater ratio in passing from one point to another; the double images within and beyond the point of vision are more separated than in the natural vision; and from these two exaggerated effects we conclude or feel that the objects are more separated than they are in nature, and that the distance or relief is greater. By magnifying more or less the stereoscopic pictures, we, by the same reason, increase less or more the stereoscopic effect. This is exemplified by looking with a double opera glass. If we look through the large lens near the eye, we considerably decrease the size of objects; and as the angle of vision remains the same as for natural vision, the eyes have to alter more their convergence, in surveying the various

planes, than they would have to do if the objects were really at the distance at which they appear to be. In looking through the eye-pieces of the same operaglass, we have a contrary effect, and a very unpleasant one, as we magnify the pictures. If they were seen by the eyes at the distance they appear to be, the angle of the optical axes would be larger than the natural angle; and the exertion in converging from one point to another of the magnified picture is less through the opera-glass than it should be if we were looking at the distance giving the same size of image on the retina. For this reason double opera - glasses are defective, and produce an incongruous sensation, which is very disagreeable. A single opera-glass is far preferable, and gives an idea of greater distance between the objects, and more relief of their various parts, than a double glass. One of the most remarkable phenomena to which M. Claudet referred, was the singular similarity of effect between squinting outwards and the stereoscope, and squinting inwards and the pseudoscope, when looking at two binocular pictures; for by squinting either way, we can bring the right and left pictures on corresponding parts of the two retina. In squinting outwards on a stereoscopic slide we have, without the stereoscope, the effect of relief and distance; and by squinting inwards, the same effect of intaglio and inverted distances we have with the pseudoscope, and by squinting vice versa we have a contrary effect. It is easier to squint inwards, as we do when looking near our nose; and to obtain, by so squinting, the stereoscopic effect in examining the two pictures, we must place the right image under the left eye, and the left image under the right eye. In so doing we have the most beautiful effect of relief and distance, and more perfect than with the instrument, because the prisms and lenses always cause a certain amount of distortion from spherical and chromatic aberration. We have also another advantage, which is, that on placing the pictures nearer or farther off, we decrease or increase at will the stereoscopic effect, or the relief and distances of the various parts of the picture. M. Claudet showed that two exactly similar

pictures placed in the stereoscope produced less relief than one of these pictures seen alone with one eye. From this fact he proves why painting can never represent the distance and relief of nature, or stereoscopic vision; that the vision with two eyes of a monocular picture gives a sensation of less relief and distance than with one eye.

THE WORK-TABLE FRIEND.

EMBROIDERED SCENT BAG.

Materials. A square of silk canvas, rather more than twice the size represented in the engraving; a skein of ombré green netting silk, one of rose ditto; a little violet, blue, and yellow netting silk; yard of white silk fringe, some white satin, pot-pourri, &c.

THE design of the wreath of flowers embroidered on this scent-bag must be enlarged to about twice the size represented in the engraving. Still further increased, and worked on kid or cloth, it is suitable for the mats now so much used as stands for the ornaments on the mantelpiece.

All the foliage, various as it is, is worked with the one skein of green silk, a needleful of the darkest part being taken for some of the leaves, the very lightest tints being selected for others, and the medium colours for the remainder. They must be worked according to the taste, and so as to produce the greatest possible varietytwo leaves of a similar tint never coming together. The leaves are done in the usual way; the veinings up the centre in half-polka stitch. Besides all the foliage, another part of the design is also worked in green-that is, all the sprays of heath, the dots of which only are worked in scarlet, in French knots. The China asters are done in shades of violet, with yellow eyes, also worked in French knots. The petals of those flowers are done by using a double thread in the needle. The forget-me-nots are worked in French knots; five blue ones forms a small circle, with a yellow one in the centre for the eye. In working the roses, begin at the heart of the flower, threading your needle so as to use the silk double. Take care that both the ends are of the same tint, either the darkest or the lightest. Having made a single French knot, with green

silk, in the eye of the flower, begin to work round it, in stitches partly laying over each other, and gradually longer, until the heart is entirely worked. The outer petals are to be done in the usual embroiderystitch, with a single thread, and in such a tint as shall correspond with the outer part of the heart of the flower.

This embroidery requires to be worked in a frame.

To make it up, fill a muslin bag, of the proper size, with any pleasant scent, and cover it again with white silk or satin. Tack on the canvas on one side, sewing it round the edges, and add the fringe.

The materials will be forwarded for 3s. 6d. ; or the embroidered square of canvas, ready for making up, for the same charge; made up, 5s.

For instructions in embroidery, see p. 326, Vol. II, new series, Family Friend.

BRIOCHE CUSHION, BRAIDED ON MERINO.

Merino, and one piece of each of four colours of Materials.-Four pieces of coloured Frenca Albert-braid.

The quantity of merino required for this cushion is three-eighths of a yard, which will cut into four pieces of the form given in the engraving. As the sections of the braid are usually all of different colours, four pieces, each containing the quantity named, will make four cushions; or if two colours only are used, two pieces will suffice for two.

The design given in the engraving is to be enlarged to the necessary size for the cushion; pricked for pointing, and then the same paper will do to mark every section. After using the paperpattern with prepared pounce, remove it,

and go over the whole design with a solution of flake white and gum water.

The braiding is to be done in the usual way, the stitches being always taken across the thin part of the braid.

In selecting the merinos, violent contrasts should be avoided. The tints should be all either dark or light. Crimsons, greens, dark blue, and claret, go well together; but if light pinks and blues are among the shades, the joining colours should be stone, drab, and a warm slate.

In arranging the braids, the same colours should be selected. Green, dark blue, or violet looks well on orange merino, orange on green or blue, pink on stone, or gray, dark blue on claret, crimson on green.

If preferred, eight pieces may be cut to form the round, instead of four; but, in any case, there should be no strong

A FASHIONABLE LADY OF THE FOURTEENTH CENTURY.-Her head was encircled with a turban, or covered with a species of mitre, of enormous height, from the summit of which ribbons floated in the air, like the streamers from the head of a mast. Her tunic was half of one colour and half of another; a zone, deeply embroidered and richly ornamented with gold, confined by her waist; and from it were suspended in front two daggers, in their respective pouches. Thus attired, she rode in the company of her knight to jousts and tournaments.-Lingard's History of England.