METHODS or I Li. IM [NATION. \) 



niiteness, high powers sliould be obtained by the 

 employment of object-glusses of short focns, and 

 low eye-pieces; but for ordinary purposes an ob- 

 ject-glass may be used with any eye-piece with 

 which it will give a cbiar, well-lit, and distinct- 

 looking image. 



It has been well observed that the illumination 

 of objects is quite as important as the glasses that 

 are employed, and the most experienced microscopists 

 have never done learning in this matter. Most 

 microscopes are furnished with two mirrors beneath 

 the stage, one plane and one concave. The first 

 will throw a few parallel rays through any trans- 

 parent object properly pbicod, and the latter causes 

 a number of rays to converge, producing a more 

 powerful effect. The first is usually used in day- 

 light, when the instru.ment is near a window, (one 

 with a north aspect, out of direct sunlight, being 

 the best;) and the second is commonly employed 

 when the source of illumination is a candle or a 

 lamp. By varying the angle of the mirror the 

 light is thrown through the object more or less 

 obliquely, and its quantity should never be sufficient 

 to pain the eye. Few objects are seen to the best 

 advantage with a perfectly direct light, and the 

 beginner should practise till the amount of incli- 

 nation is obtained which produces the best effect. 

 It is advisable that the hole in the stage of 



