2O6 



PRACTICAL MICROSCOPY. 



The most important point to be remembered in the use 

 of these reflectors is the proper management of the light. 

 Perhaps the student will fail at first in seeing together the 

 pencil and the object, but this difficulty will vanish upon 

 securing the proper illumination. The light must not be 

 concentrated too strongly upon the object, neither should 

 the paper be placed entirely in the shade, the student soon 

 arriving at the happy medium after a few trials. 



FIG. 189. 



In order to obtain the same degree of amplification upon 

 the paper as appears when looking down the tube of the 

 instrument, the paper must be placed at the same distance 

 from the camera-lucida as that accessory is situated from 

 the objective front ; but the magnification is generally 

 expressed at a distance of 10 inches. 



Another form of this instrument is Nachet's, for use with 

 vertical microscopes, with the ordinary pattern when used 

 vertically with immersion lenses or in any other position of 

 the instrument. 



