5. Owing to the exposure of the eye and every part of the apparatus to light, the eye itself is unfitted for distinct vision, and the binocular pictures become indistinct, especially if they are Daguerreotypes,[34] by reflecting the light incident from every part of the room upon their glass or metallic surface. [34] Mr. Wheatstone himself says, “that it is somewhat difficult to render the two Daguerreotypes equally visible.”—_Phil. Trans._, 1852, p. 6. 6. The reflecting stereoscope is inapplicable to the beautiful binocular slides which are now being taken for the lenticular stereoscope in every part of the world, and even if we cut in two those on paper and silver-plate, they would give, in the reflecting instrument, _converse_ pictures, the right-hand part of the picture being placed on the left-hand side, and _vice versa_. 7. With transparent binocular slides cut in two, we could obtain pictures by reflection that are not converse; but in using them, we would require to have two lights, one opposite each of the pictures, which can seldom be obtained in daylight, and which it is inconvenient to have at night. Owing to these and other causes, the reflecting stereoscope never came into use, even after photography was capable of supplying binocular pictures. As a set-off against these disadvantages, it has been averred that in the reflecting stereoscope we can use larger pictures, but this, as we shall shew in a future chapter, is altogether an erroneous assertion. _Description of the Lenticular Stereoscope._ Having found that the reflecting stereoscope, when intended to produce accurate results, possessed the defects which I have described, and was ill fitted for general use, both from its size and its price, it occurred to me that the union of the dissimilar pictures could be better effected by means of lenses, and that a considerable magnifying power would be thus obtained, without any addition to the instrument. [Illustration: FIG. 11.] If we suppose A, B, Fig. 11, to be two portraits,—A a portrait of a gentleman, as seen by the left eye of a person viewing him at the proper distance and in the best position, and B his portrait as seen by the right eye, the purpose of the stereoscope is to place these two pictures, or rather their images, one above the other. The method of doing this by lenses may be explained, to persons not acquainted with optics, in the following manner:—