For opake objects, you take away the slider-holder, K; place on the stage either the concave glass, _s_, or the nippers, _b_; screw the concave speculum, _e_, to the arm, _a_, which place on the stage with the arm in the hole, I. The light is now to be reflected into this concave dish from one of the mirrors, O, below, and it will thus be strongly condensed upon the object. With this concave speculum any of the magnifiers in the wheel, P, may be used. When the single silver concave, _f_, is used, it is screwed to the arm C D, and the one, _e_, and arm, _a_, are not then applied. For further directions for the management of microscopes, the light, &c. see Chap. IV. p. 129, and sequel. A DESCRIPTION OF CULPEPER’S, OR THE COMMON THREE-PILLARED MICROSCOPE. Plate IV. Fig. 3. The only recommendations of this original instrument are, its simple construction and lowness of price. It gives a pleasing view of the object. It is precluded by its form from some of the advantages of the two foregoing instruments, because both the stage and the mirror are confined. This microscope consists of a large exterior brass body, A B, supported on three brass scrolls, which are fixed to the stage F; the stage is supported by three larger scrolls that are screwed to the mahogany pedestal G H. There is a drawer in the pedestal which holds the apparatus. The concave mirror, I, is fitted to a socket in the center of the pedestal. The lower part, B, of the body forms an exterior tube, into which the upper part of the body, C, slides, and may be moved up or down by the hand, so as to bring the magnifiers which are screwed on at D, nearer to, or further from the object. A LIST OF THE APPARATUS TO CULPEPER’S MICROSCOPE. Five magnifiers, each fitted in a brass cell; one of these is seen screwed on at D. Six ivory sliders, _k_, five of them with objects; and a small ivory box, _m_, containing some spare talcs, and wires for them. A brass tube, N, to hold the concave speculum. A brass box, M, for the same speculum. A fish-pan, _c_. A set of glass tubes, _b_. A flat and a concave glass, both fitted to the stage. A brass cone, _g_, to exclude superfluous light; it applies at the under side of the stage, F. A brass box, _p_, with plane and concave glasses for living objects. A pair of forceps, _q_. A steel wire, _b_, with a pair of nippers at one end, a point at the other, and a small ivory cylinder, _h_, to fit on the pointed end of the nippers. A convex lens, E, moveable in a brass semicircle; this is affixed to a long brass pin, which fits into a hole, F, on the stage. The uses of the above apparatus have been sufficiently described in the preceding pages. TO USE THIS MICROSCOPE.