P the tube for holding the lens K, with an inner tube, which is forced upwards with a spiral spring. The sliders are thrust between the plates h and i. The lower end of P goes into the hole n in the stage. The hollow part at k is intended to receive a glass tube N.
R is a brass cone, which is occasionally put in the bottom of the cylinder P to intercept the light.
S is a box, with a concave and a flat glass for con fining small living insects. It is placed upon the hole n.
T is a flat glass to lay objects upon, and u a concave one for fluids.
O is a pair of pliers and a sharp point ; and Z a brush, as formerly described.
NV is a round ivory box, for holding circular pieces of mica, and rings for the sliders.
? is a small ivory cylinder, which goes upon the pointed end of the steel wire O.
'NI a fish•pan for holding small fishes, in order to view the circulation of the blood. The tail is spread across the oblong hole at the small end k, and tied firmly by a ribbon fixed to it. The knob 1 is to be put through the slit in made in the stage, and the tail may be brought below the end C of the micro scope.
X is a wire, by which the glass tubes are cleaned.
In using this microscope, screw the proper magnifier to the end C, place the tube P in the hole n, and slip one of the ivory sliders between the plates h and i. Make the upper edge of the bar DE coincide with the division, having the same number with the magnifier used, and fix it firmly by the nut O. Light being thrown upon the object by the mirror G, apply the eye to the upper end of the microscope, and obtain distinct vision by means of the adjusting screw e g.
When the objects are opaque, remove the tube P, and having placed the object on a flat glass u under C, or upon one end of the jointed pliers o p, screw the con cave silver speculum to the end of the cylinder L, and slide this cylinder on the lower part EC of the tube, so that the upper edge of L may coincide with the same number as the number of the magnifier employed. Re flect the light employed from the mirror G upon the speculum h, and it will be again reflected from the spe culum upon the side of the opaque object next the eye.
11. Universal Compound Microscope.
One of the most complete and commodious compound microscopes is represented in Plate CCCLXXVII. Fig. 20. where AB is the body, the eye-glasses being contain ed in an inner sliding tube, by which their distance from the glass at B can be increased or diminished, and the magnifying power of the instrument altered. The body AB is attached by a screw to the arm CD, which may be moved through a square socket over the object. The stage NIS moves up and down the square bar EF by means of the rack and pinion AI ; and this bar, with all its accompanying apparatus, moves round a joint at the top of the great pillar V, supported upon the three feet G, G, H. By the aid of this joint, the microscope may be put into a horizontal, a vertical, or an oblique direc tion. At the stage NIS is a sliding brass spring N for
confining slips of glass, or large sliders, when the mi croscope is to be used out of the horizontal position. The lens U is intended to concentrate or modify the light re flected from the mirror G, and it may be adjusted to a proper distance by means of two small screws, one of which is seen at u. In candle light this lens is of great use, and it may be turned aside on a joint when it is not required. Six magnifying lenses are set in a brass wheel, screwed in a circular box P. The wheel may be moved round its centre by the ac tion of the finger on its milled rim, and it stops by a click the instant that any of the magnifiers comes into its exact position in the axis of the other lenses. The lenses are numbered from one to six, and the proper number appears in a small opening made in the upper side of the box P. This box screws into the arm CD, and may be taken of when required. If we unscrew the body AB, the intsrument becomes a single micro scope by looking directly through any of the lenses in the wheel. The mirror 0 may be moved up or down the bar EF, by pushing against the screw at r. In ad dition to the apparatus already described, as belonging to single microscopes and to Cuff's compound micro scope, the following may be enumerated. A moveable stage \V, which is applied to the hole S of the stage by the pin a, and has thus a horizontal motion under the field of view. A very deep concave lens r is fitted to the large hole of this stage, and also the concave and plane glasses s and o, while to the small holes x, x, a black and white piece of ivory Iv is fitted for opaque ob jects, and a concave and plane glass similar to o and S. The arm CD is sometimes furnished with rack work, to turn the pinion above, so as to move the magnifiers in the most accurate manner over the objects ; and the stage NIS is sometimes jointed, in order to turn by a screw and teeth in a horizontal direction. In using this microscope, the slider•holder K, containing a slider of objects, is placed in the stage NIS, and the arm CI) is moved in its socket, tilt a mark on the side is brought to the edge of the socket. The arm is then turned, till the magnifier is directly over the object, (hi.: eye being then placed at the upper end of the tube AB, and the light reflected strongly up into it from the mirror 0. The pinion Al is then turned to the right or left till the object is seen in the most distinct manner. When the objects are opaque, the slider-holder K is removed, and either the concave glass, or the jointed pliers, are placed on the stage. The concave silver speculum e is then screwed into the arm a, which is placed on the stage, with the cylindi ical part passing through the hole I ; and the light being reflected upon the speculum from the mirror 0, it will be strongly condensed by it, and thrown upon the opaque object.