ARTIFICIAL LIGHT. 187 



nochromatic illumination we have ever tried, and the 

 resolutions are quite as strong and effective as when the 

 cupro-ammonia cell is used in the usual manner. In 

 working with sunlight by either of the methods de- 

 scribed, care should be taken to exclude the full strength 

 of the solar beam ; that is, if the sun be clear and bright. 

 Too much light, supposing the manipulations are tolera- 

 bly well attended to, will be manifest by the appearance 

 of a multitude of diffraction lines, and these as a rule 

 may be recognized by their extending beyond the ob- 

 ject observed. Under very high amplifications, involv- 

 ing the use of powerful eye-pieces, we can of course 

 help ourselves to a little more of the solar beam. When 

 the sun is very clear, the beam being condensed on the 

 top of the cover, as above described, there is danger 

 sometimes, if the object be balsam mounted, of the heat 

 starting the balsam. In this way we once ruined a 

 Moller probbe plate. A very little attention will, how- 

 ever, provide against accidents of this nature. 



ARTIFICIAL LIGHT. 



For the ordinary purposes of the microscopist the St. 

 Germain or German Student's Lamp, 0. A. Kleemann's 

 patent, or a similar lamp made by the Cleveland Com- 

 pany, will be found quite satisfactory. This style of 

 lamp is too well known to require any extended descrip- 

 tion. The flame is bright, clear and intense, and its 

 height can be changed at will. It is easily kept in 

 order, and has the advantage, too, of being well adapted 

 for ordinary household purposes. The breakage of 



