When ordinary daylight is employed for this purpose, a dark slide will be required for the prepared plate, in the same way as for photographing landscape, &c. These dark slides are generally made by each individual to suit his particular arrangements of negatives, &c.; but it may be here recommended that the operator should always focus in the same slide which he is about to use, as so small a difference in distance lies betwixt perfection and failure. For an ordinary student, perhaps the above method is that which is the most readily used, and consequently the most generally available; but almost every one has a different arrangement of microscope, &c., by which he procures these minute pictures. Mr. Shadbolt (one of our most successful photographers) gives the following instructions:--“Having removed the upper stage plate of a large compound microscope, I replace it with one of wood, supplied with guide pins of silver wire, in order to admit of its supporting a slip of glass coated with collodion, and excited in the nitrate of silver bath in the usual way. If the ordinary brass stage plate were left undisturbed, it is obvious that it and the excited slip of glass would be mutually destructive. “The microscope is now to be placed in a horizontal position, the objective, intended to produce the picture, made to occupy the place usually filled by the achromatic condenser on the _sub-stage_ of the microscope, while _another_ objective is screwed into the lower end of the body of the instrument, which is used not only to focus with, but also to make the requisite allowance for actinic variation. “The negative intended to be reduced is then arranged vertically, with its centre in the axis of the microscopic body, at a distance of from two to four feet from the lower object-glass, and with a convenient screen of card, wood, or thick paper, to cut off any extraneous light that would otherwise pass beyond the limits of the picture. “A small camphine-lamp is employed for the purpose of illuminating the negative, having a good bull’s-eye lens as a condenser, so arranged with its flat side next the lamp that the refracted rays shall just fill the whole of a double convex lens of about six inches in diameter, the latter being placed in such a position as to refract the rays of light in a parallel direction upon the negative. By this arrangement the _bull’s-eye lens_ of about two inches and a half in diameter _appears_ as the source of the light instead of the small flame of the lamp. “By using a bat’s-wing gas-burner of a good size, a _single_ lens, instead of the two, may be so placed as to give the necessary uniformity of illumination.” This arrangement requires the same care in working as that before mentioned, the pictures being produced, developed, and fixed by the same treatment.