1 68 



THE AMERICAN MONTHLY 



[September, 



TJie Polari-Spectro-JIicroscope. 



This instrument is a combination 

 of microscope, spectroscope and pc- 

 lariscope, by means of which certain 

 optical properties of bodies can be 

 studied with far more delicacy than 

 by any other means. It was devised 

 by Dr. A. RoUet, of Gratz. Fig. 27 

 represents the instrument complete ; 

 fig. 28 is a section of the apparatus 

 beneath the stajre. 



i'ULAKl-SJ'ECTKO MlCKObCUl'li. 



In the ordinary micro-spectroscope 

 the image of an object slightly out 

 of focus is received upon the narrow 

 slit of the spectral-ocular, and a nar- 

 row band of that image is examined 

 through the prisms. In this way the 

 absorption-bands can be studied per- 

 fectly well in the case of the greater 

 number of objects. But only very 

 minute portions of an object can be 

 studied in this way. Before the si:)ec- 

 troscopic oculars were introduced, 



the plan was to throw a spectrum, or 

 a part of a spectrum, into the field of 

 the microscope along with the object, 

 and to study the object in the dilTer- 

 ent colors — in monochromatic light. 

 This is the plan adopted in this in- 

 strument. The spectrum is formed 

 by the prisms^^ (fig. 28) the slit being 

 at s, and projected into the field of 

 view by the lens g. With an objec- 



FlG. 2S. 



tive of medium power the entire spec- 

 trum can be seen at one time. The 

 object may be moved across the spec- 

 trum by the stage movements, or, by 

 means of the screw r (fig. 27), the spec- 

 trum can be moved laterally over the 

 object. For examinations in mono- 

 chromatic light this is the only appa- 



ratus rccpMred ; but the p.urpose of 

 this instrument seems to be rather to 

 examine the conduct of objects with 

 polarized light, and especially to dc- 



