The foregoing pieces constitute the several parts necessary for viewing opake objects. We shall now proceed to describe the single microscope, which is used for transparent objects; but, in order to examine these, the box, H I K L, must be first removed, and in its place we must insert the tube, Y, of the single microscope, Fig. 2, now to be explained. Fig. 2 represents a large tooth and pinion microscope; at _m_, within the body of this microscope, are two thin plates that are to be separated, in order to let the ivory sliders, Fig. 7, pass between them; they are pressed together by a spiral spring, which bears up the under plate, and forces it against the upper one. The slider, Fig. 3, that contains the magnifiers, fits into a hole at _n_; any of the magnifiers may be placed before the object, by moving the aforesaid slider: when the magnifier is at the center of the hole P, a small spring falls into one of the notches which is on the side of the slider, Fig. 3. At _h_, slides a condenser, Fig. 4, for condensing the sun’s rays, and enlarging the field of view on the screen: the number must correspond with that of the magnifier used. This microscope is adjusted to the focus, while exhibiting the object, by turning the milled nut O. APPARATUS TO THE OPAKE SOLAR MICROSCOPE. The mirror O P, Fig. 1, and square plate, and the tubular body of the microscope, A F. The opake box and its tube, I K G. The tooth and pinion or single microscope, Fig. 2. The slider of magnifiers, Fig. 3. The megalascope magnifier, Fig. 6, fitted to P of Fig. 2. Six ivory sliders with transparent objects, Fig. 7. Twelve wood sliders with opake objects, and a brass frame to hold them, Fig. 5. A brass square-formed slider case, Fig. 8, to hold any animal, piece of ore, or other opake object, and is to be placed like the other slider at H, Fig. 1. A pair of nippers and point, Fig. 9, the pin, _a_, of which fits into the hole of the slider, Fig. 4, and holds before the magnifiers at P, Fig. 2, any small fly or other complete object to be magnified. A four-glass slider in a brass frame, Fig. 10, for any animalcula, &c. to be placed between the plates at _m_, Fig. 2. A set of glass fish tubes, Fig. 11. A pair of forceps, Fig. 12. Two brass nuts for the window-shutter or board, Fig. 13; and the two brass fastening screws, _d e_, Fig. 1, which may be either used with or without the above two nuts. The figures on the plate are about half the original size, and the apparatus now made by Messrs. Jones packs into a case thirteen inches long, nine inches broad, and four inches deep. For price, see the list at the end. TO USE THE SOLAR MICROSCOPE.