At the stage N I S, is a sliding brass spring, N, serving to confine down slips of glass or large sliders, when objects placed thereon are intended to be viewed out of the horizontal position of the stage. A lens, U, called the condensing lens, fixed in a frame connected to a socket, is for condensing and modifying the rays of light reflected from the concave or plane mirror, O, below; it may be set to a proper distance by raising it up by two little screws, one of which is shewn at _u_. This lens is of considerable use by candle-light, as it serves to fill the whole body, A B, beautifully with light on the object. It is turned aside on a joint pin, when not in use. Six magnifiers are contained in the wheel at P, as in the former microscope. The mirrors, O, below may also be slid upwards or downwards on the stem, by pushing against the screws at _r_. Thus the stage, lens U, and mirrors below, being all in one axis of motion, admit the adjustment of the distinct view, light, &c. in the most accurate and pleasing manner. When the instrument is packed into its case, the feet, G G H, may all be folded together as one, and the body A B, screwed off, for the advantage of being portable. The body, as screwed off, leaves the instrument a single microscope.
THE GENERAL APPARATUS TO THIS MICROSCOPE IS AS FOLLOWS.
First, such as accompany the preceding microscope. The brass wheel with magnifiers, P, Fig. 2. The slider-holder, K. The brass pin and arm, _a_, for receiving the concave speculum, _e_, which is applied to the upper side of the stage, and used common to all the magnifiers. The silver concave speculum, _f_, with a magnifier set therein, used by itself in the arm C D. These two speculums form the instrument into what is called an OPAKE MICROSCOPE.
A brass cone, g, fitting the under side of the stage, N I S, to exclude superfluous light. The illuminator, or convex lens, _d_, Fig. 1, fitted to T of the stage. The jointed nippers, _b_, fitted to the stage, and either on the point or nippers to hold any small insect, or other opake object. An ivory black and white piece, _h_, is also fitted to the point to contrast the colour of any object laid thereon; the light upon this is reflected from the silver concaves placed above, which reflect the light downwards received from the mirrors at O. Six ivory sliders as shewn at _i_, containing a selection of objects, placed between Muscovy talc, and fastened by spring wires; and a brass frame slider, _k_: all for the stage, K, when in use. A set of glass tubes for fish or liquids, _l_, to be filled with water and stopped with cork, for the slider-holder K. A pan, _c_, for fish or frogs, fitted to the stage at S. A small ivory box, _m_, with spare talcs and wires. The explorator, _n_, a lens set in a brass cell, for viewing the larger sort of objects either by the hand, or from the arm C D, Fig. 2. A plane glass, _o_, and a concave ditto, _s_, both fitted to the hole of the stage, N I S, for viewing fluids, and confining the animalcula, &c. between them, and so forming what is called the AQUATIC MICROSCOPE.