Hi i>i \KTIN. 47 



A MICROSCOPE FOR TH, RAPID C'-IAI\IGII\IG FROM PLANE TO 

 POLARIZED L VICE VERSA. 



BY C O. HARKIS. 



'■■"The iiiicro-polariscope or poi;ifi/Ar ;s a polariscope used in con- 

 iic'c'tion with the microscope. The luosl. couunon and typical forms 

 •consist of two prisms, that is, two somewhat elongated rhombs of Ice- 

 land spar and cemented together wi i ';)iiada ualsam. 



''These nicol prisms arc then mounted in such a way that the light 

 passes through tliem lengthwise, and in passing is divided into two 

 rays of plane polarized light. 



"Polarizer and Analizer. — The polarizer is one of the nicol prisms. 

 It is placed beneath the object, and in this way the object is illumi- 

 nated with polarized light. The analizer is the other nicol and is- 

 placed at some level above the object very convenient above the ob- 

 jective." 



The application of polarized light in the microscopic examination 

 of foods and feeds is indispensable. Its importance, however, is not 

 as yet fully recognized by many chemists. 



The chemist many times in examining a product has to resort to 

 the differences existing between the starch gTanules of different sub- 

 stances for his final conclusions. Many starches differ greatly in 

 size, shape, hilum, action towards certain reagents and polarized 

 light. There are exceptions to this, and in examining foods we some- 

 times find different starches resembling each other closely in size, 

 shape, and action tow^ards certain reagents. When such a case pre- 

 sents itself we generally get a clearer insight into the product by 

 using polarized light. 



It is very seldom we find different starches in the same mixture 

 that polarize alike. So polarized light is what we resort to in the end. 



The ordinary continental microscopes do not have the micro-polari- 

 scope readily adjustable. When using polarized light with these 

 instruments considerable time is lost in changing from plane to polar- 

 ized light. 



The microscope shown in this cut was designed by the writer to save 

 as much time as possible in changing from plane to polarized light, 

 and vice versa. 



The instrument is constructed with two substages instead of one, 

 the regular one (1) for the abbs condenser and the other (2) for the 

 polarizer. The polarizer so arranged can be thrown into the optical 

 axis at will. The analizer (3) or other nicol prism is mounted as in 

 petro-graphical instruments, the prism being placed in the draw-tube 



» Gage. 



