200 MICROSCOPIC ILLUSTRATIONS. 



The direct light of the sun is utterly improper for 

 exhibiting opaque bodies, being polarized and decom- 

 posed by them, so as to give rise to all sorts of optical 

 deceptions : neither can it be modified or dulled by 

 refraction through rubbed glass, or any sort of semi- 

 pellucid substances, and thus rendered fit for use : by 

 reflection from white unpolished surfaces it may, but it is 

 then no stronger than the light of the atmosphere. 



6th. Method of observing Opaque Objects by Day -light, 

 plain or condensed. Employ the mounting (No. 2) recom- 

 mended for transparent objects by artificial light. 



If your object is contained in a slider, insert it into the 

 holder in the usual manner : turn your back diagonally 

 towards the window, and place the engiscope on a table, 

 in a convenient position for observation in that direction, 

 so that the light of the window may fall full upon your 

 object, without being intercepted by your head : the 

 nearer you are to the window the better, provided its 

 direct light does not get into your eyes. You then pro- 

 ceed to the adjustment of the focus, &c. as before de- 

 scribed. If your power is considerable, or the day dull, 

 you will require a condensed light : to obtain it, attach 

 the condenser, 'f 9 to the neck of the body, by means of 

 its clamping screw and split socket, 'g / unscrew the 

 double convex lens from the other, and remember to use 

 only the piano convex, with its plane side presented 

 towards the light, and its convex side towards the object : 

 slide it up or down upon the neck of the body; and adjust, 



