It will be obvious to the reader from the preceding description that it must be put together as represented in the figure; that he has to place the slider-holder, K, to the stage, N I S, with one slider of objects; to reflect as strong a light as possible from the concave mirror, O, below, by turning it into the best position, and moving it upwards or downwards all the while he is looking down the body, A B. Then, for a distinct view of the object, to turn the pinion, M, in a slow and gentle manner. A small degree of practice will render the management very familiar. For opake objects, the slider-holder, K, is to be removed; the silver speculum, _e_, screwed to the arm, _a_, and by its pin placed in the hole, I, of the stage, with the concave part downward above the stage; the glass, _o_, or the nippers, _b_, with ivory, _h_, placed at the stage: then the light reflected from the mirror, O, up to the speculum above, which will again reflect the light very strongly upon the object. Practice also in this case can make it easy to the beginner. The use of the rest of the apparatus has been sufficiently explained. OF THE MOST IMPROVED COMPOUND MICROSCOPE, BEING UNIVERSAL IN ITS USES, AND FORMING THE SINGLE, COMPOUND, OPAKE, AND AQUATIC MICROSCOPES. A person much accustomed to observations by the microscope, will readily discern the several advantages of this instrument over the preceding one. Besides its containing an additional quantity of useful apparatus, it is more commodious and complete for the management while observing, as it may instantly be placed in a vertical, oblique, or horizontal situation, turned laterally at the ease of the observer, and the objects viewed by the primary direct light, or reflected as usual, at pleasure. These particulars the following description will clearly shew. I shall not again so fully describe the same apparatus, as the reader must already understand their uses from the preceding references.