50 THE MICKOSCOPIST. 



will serve this end as well as modify the quality of the 

 light. For very delicate observations a dark shade over 

 the stage, which may be fastened by an elastic ring to 

 the microscope-tube, so as to shut off extraneous light, 

 will be useful. 



Table, etc. The microscopist's work-table should be 

 large and massive, so as to be convenient and free from 

 vibration. Drawers for accessories and materials used in 

 preparing and mounting objects are also desirable, as well 

 as a few bell-glasses for secluding objects from dust. Re- 

 agents should always be removed from the table after use 

 and kept in another place. 



Light. Dr. Carpenter has well said, " Good daylight is 

 to be preferred to any other kind of light, but good lamp- 

 light is preferable to bad daylight." A clear blue sky 

 gives light enough for low powers, but a dull white 

 cloudiness is better. The direct rays of the sun are too 

 strong, and should be modified by a white curtain, reflec- 

 tion from a surface of plaster of Paris, or, still better, by 

 passing through a glass cell containing a solution of am- 

 monio-sulphate of copper. 



Various kinds of lamps have been contrived for micro- 

 scopic use ; among the best are the German and French 

 " student's reading lamps," which burn coal oil or petro- 

 leum. It is often useful to moderate such a light by the 

 use of a chimney of blue glass, or by a screen of blue glass 

 between the flame and the object. Dr. Curtis contrived 

 a useful apparatus, consisting of a short petroleum lamp 

 placed in an upright, oblong box. On one side of the box 

 is an opening occupied with blue glass ; on another side 

 the opening has ground-glass, as well as a piece colored 

 blue, and a plano-convex lens so placed as to condense the 

 light thus softened to a suitable place on the table. 



As a general rule the light should come from the left 

 side, and that position assumed or inclination given to the 

 instrument which is most comfortable to the observer. 



