MICROSCOPES FOR USE IN CHEMICAL LABORATORIES 71 



are sent through the preparation upon the stage by means of 

 the mirror M. The analyzer consists of a prism sliding in and 

 out of the microscope 

 tube at A. In the 

 illustration the dotted 

 lines indicate the ap- 

 proximate direction of 

 the light rays used to 

 illuminate the object. 

 When moderate tem- 

 peratures are neces- 

 sar.y the objective 

 must be cooled by 

 means of a blast of 

 air directed upon the 

 lower lens, and when 

 high temperatures are 

 employed the objec- 

 tive must be water- 

 jacketed. 



Binocular Micro- 

 scopes. Grccnough 

 Type. — No laboratory 

 which is concerned 

 with problems involv- 

 ing industrial micros- Fig. 29. Simple Form of Hot-stage Microscope. 

 conv or with trip Polarized Light is obtained by Reflection from 



' . the Plates P and R and the Mirror M as indicated 



qualitative examina- by the Dotted Arrows. A = Analyzer. B= Small 



tion of fragments of Gas Burner which swings under the Stage Opening, 

 material detached 



from fairly large masses of matter, can be considered as satis- 

 factorily equipped unless it includes a binocular microscope 

 of the Greenough type. The marvelously long free working 

 distance of the double objectives of these instruments, their 

 remarkable penetrating power, the fact that the images of the 

 object being studied stand out with stereoscopic distinctness 

 and are right side up instead of inverted, the adaptability of 



