120 
ELEMENTARY CHEMICAL MICROSCOPY 
In the absence of an arc lamp use a 400-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 ^ 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¬ 
strument for the study of ultra- 
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 
^ Cotton et Mouton, C.r., 136 (1903), 1657; Les Ultramicroscopes, Paris, 1906; 
J. Roy. Micro. Soc., 1903, 573; Lemanissier, Corps Ultramicroscopiques, These, 
Paris, 1905, 21. 
Fig. 59- The Ultramicroscope of 
Cotton & Mouton. 
