120 ELEMENTARY CHEMICAL MICROSCOPY 



In the absence of an arc lamp use a 4oo-watt Mazda lamp 

 with concentrated filament. Or if gas alone is available, employ 

 an inverted Welsbach incandescent mantle or even better an 

 acetylene light. 



Be sure that the reflecting condenser is high enough in its 

 mounting to just touch the object cell upon the stage. Substage 

 ultracondensers are usually screwed into their tubular mountings 

 and are easily turned up or down to permit of their accurate 

 adjustment. 



The cardioid ultramicroscope is restricted to the study of 

 liquids, to the search for bacteria not readily demonstrated by 

 the paraboloid condenser and to the examination of thin textile 

 fibers, and such other thin semitransparent and flexible solid 

 fragments as will permit pressing out flat, and whose thickness 

 will then be no greater than the thin liquid film of the medium 

 in which they are immersed. 



Cotton and Mouton's Ultramicroscope 1 consists of a special 

 prism consisting of a rectangular prism of glass having an in- 

 clined face. This prism is laid 

 upon the stage of the microscope 

 and serves for the projection of 

 an oblique beam of light into the 

 preparation placed upon its upper 

 surface. The diagram, Fig. 59, 

 will make clear the construction 

 and the method of using. The 

 prism P, 8 to 10 millimeters 

 high, which converts an ordinary 

 compound microscope into an in- FlG - 59- The Ultramicroscope of 

 strument for the study of ultra- Cotton & Mouton - 



microscopic particles, rests upon the stage S. The liquid L, to 

 be studied, is placed upon an ordinary glass object slide s and 

 covered with a thin cover glass c. A drop of homogeneous im- 

 mersion oil is placed upon the top of P, and the preparation is 



1 Cotton et Mouton, C.r., 136 (1903), 1657; Les Ultramicroscopes, Paris, 1906; 

 J. Roy. Micro. Soc., 1903, 573; Lemanissjer, Corps Ultramicroscopiques, These, 

 Paris, 1905, 21. 



