MICROSCOPES. 229 



which must be first screwed into the arm, D, and it is ready 

 for use. Now push the slider with transparent objects 

 between the stage and a spring plate which is under it, turn 

 your face to the light, and while looking through the micro- 

 scope, turn the mirror so as to reflect the light up to the eye 

 through the body of the microscope, then turn the nut till 

 you have a distinct view of the object in the slider. For 

 opaque objects the mirror in this microscope is of no use, 

 but you must let as much light as possible fall on their sur- 

 face. There are three magnifiers of different foci belonging 

 to this microscope : that which has the largest aperture is 

 the least magnifier ; they may be used singly, or either two 

 of them may be screwed together, or all three, making in 

 this way seven different powers, the compound power of 

 which magnifies about 18,000 times. 



To use it as a Single Microscope. Unscrew the body, 

 A, B, c, from the magnifier, and follow the foregoing direc- 

 tions, particularly observing, in examining opaque objects, 

 not to shade them from the light by the head or any part 

 of the dress. 



N. B. This microscope is also fitted up with the part, w, 

 for condensing the light from a lamp or candle upon the 

 object ; likewise with a joint at the base of the pillar, so 

 that it can be set at any angle, being much more pleasant to 

 use than when perpendicular ; also with tripod folding feet, 

 and joint mounted with doublets or achromatics. R is an 

 extra power, or one of Dr. Wollaston's doublets, or an 

 achromatic. Price, $15.00. 



Directions for using the Compound Microscope. (Fig. 751, 

 next page.) A, B, c, represent the body ; a middle and a 

 double eye glass are contained in the tube which slides in 

 the part A, which is made to slide easy, so that a finer 

 adjustment may be obtained than by sliding the body alto- 

 gether, when it is set near the focus ; and the further it is 

 drawn out the greater the power : M is a concave mirror, 

 which must be turned so as to reflect the light up the body 

 of the microscope : N is a slider (with objects) to be placed 

 between the stage, s, and the spring plate : three sliders 

 are sent with this instrument. Care must be taken not to 

 shade the light from the mirror with the slider, which may 

 be avoided by placing the slider any otherwise than straight 

 VOL. IT. 20 



