THE MICROSCOPE. 



37 



mining the light through pale blue^glass. A plate of it 

 may be placed on the stage of the microscope, or a blue 

 chimney may be put on the lamp. Although the light is 

 softened thereby, it is, however, at the expense of illumi- 



FIG. 34. Darwin's dissecting microscope. 



nating power, and therefore sometimes, with very high 

 powers, the yellow flame has to be employed. 



An Argand gas-burner may be used, and answers re- 

 markably well if covered with a blue chimney. The light 

 from a colza oil or a belmontine lamp is, however, softer. 

 An ordinary colza oil reading lamp does extremely well ; 

 but if a special lamp has to be procured, a lamp for burn- 



