MICROSCOPES. 233 



ination : R, a pair of tongs for taking up any small object : 

 s, a small box for holding a little talc, and rings to replace 

 objects in the slides : T, a slider for holding objects, six of 

 which are sent with the microscope : u, a slip of glass used 

 to lay any objects on, and particularly useful in viewing ani- 

 malculae and the crystallization of salts : w, a glass tube to 

 confine a small fish, water-newt, or tadpole, for viewing 

 the circulation of the blood : x, is a pair of forceps for con- 

 fining objects, they are opened by pressing the small studs 

 between the thumb and finger : the other end of the wire 

 is pointed for sticking objects on ; a small ivory cylinder is 

 fixed to this end, it serves also as a handle to turn the for- 

 ceps about, and also for laying any very small objects on. 

 The magnifying power of this instrument is with the 

 No. 1. 22,500. No. 4. 1,600. 



2. 8,100. 5. 900. 



3. 3,600. t 6. 450. 



To use the Microscope. Screw the magnifier you intend 

 to use to the bottom of the body at E ; the readiest way of 

 doing this is to draw the body entirely out of its spring 

 tube ; push one of the sliders with transparent objects be- 

 tween the stage and a spring plate which is under it; face 

 the light, and while looking through the microscope, turn 

 the mirror so as to reflect the light upwards to the eye at 

 A. The part c, has the same Nos. engraved on it as the 

 magnifiers, which must be set to correspond with the mag- 

 nifier in use ; then by turning the nut, Y, a fine adjustment 

 may be obtained. There is a certain direction of the mirror 

 m which the object appears better than in any other, and 

 which may be easily discovered with a little practice. In 

 the examination of opaque objects, the mirror is of no use, 

 but the surface must be enlightened as much as possible ; 

 this can be very well performed in this microscope by 

 directing the rays of the sun, or a candle, through the con- 

 vex lens, i, on the object; for this purpose the lens is to be 

 fitted to the stage, and if a candle be used, it must be placed 

 so as to refract the light through the lens strongly on the 

 object. A few trials will make it easy, as the lens may be 

 turned any way, or raised and lowered in its frame. By 

 day and without the sun this lens is of no use, so that opaque 

 objects can only be enlightened by placing the microscope 

 in a good light, and it will not be possible to magnify them 

 20* 



