Now place the object either on the stage, or in the nippers L, and in such a manner, that it may be as nearly as possible over the center of the stage; bring the speculum, F, over the part you mean to observe; then get as much light on the speculum as you can, by means of the mirror, I; the light received on the speculum is reflected by it on the object. The distance of the lens, F, from the object is regulated by moving the pin, D, up and down, until a distinct view of it is obtained. The rule usually observed is, to place the lens beyond its focal distance from the object, and then gradually slide it down, till the object appears sharp and well defined. The adjustment of the lenses to their foci, and the distribution of the light on the object, are what require the most attention. These microscopes are sometimes fitted up with a rack and pinion to the pillar A, and pin D, for the more ready adjustment of the glasses to their proper foci. DESCRIPTION OF LYONET’S ANATOMICAL MICROSCOPE. Plate VI. Fig. 3. Fig. 3 represents the instrument with which M. Lyonet made his microscopical and wonderful dissection of the chenille de saule or caterpillar of the goat moth,[36] of which a specimen is given in Plate XII. Fig. 1, &c. of this work. This portable instrument needs no further recommendation. By it, other observers may be enabled to dissect insects in general with the same accuracy as M. Lyonet, and thus advance the knowledge of comparative anatomy, by which alone the characteristic, nature, and rank of animals, can be truly ascertained. [36] Phalæna cossus. Linn. 63. A B is the anatomical table, which is supported by the pillar O N; this is screwed on the mahogany foot, D C. The table A B, is prevented from turning round by means of two steady pins; in this table or board there is a hole, G, which is exactly over the center of the mirror, F E, that is to reflect the light on the object; the hole, G, is, designed to receive a flat or a concave glass, on which the objects are to be placed that you design to examine or dissect. R X Z is an arm formed of several balls and sockets, by which means it may be moved in every possible position; it is fixed to the board by means of the screw, H; the last arm, I Z, has a female screw, into which a magnifier may be screwed, as at Z. By means of the screw, H, a small motion may be occasionally given to the arm I Z, for adjusting the lens with accuracy to its focal distance from the object. Another chain of balls is sometimes used, carrying a lens to throw light upon the object; the mirror is also so mounted, as to be taken from its place at K, and fitted on a clamp, by which it may be fixed to any part of the table, A B.