116 The Microscope. 



NOTES ON THE MICROSCOPE STAND AND ON SOME OF 

 ITS ACCESSORIES. 



THE USE OF THE MICROSCOPE. 



AN AMATEUR. 



XVII. 



DO not handle the mirror too daintily ; if well mounted there 

 is little danger of injuring it, and a firm grasp makes it 

 more easily manageable. At first there will probably be some 

 difficulty in illuminating the field as it should be illuminated, 

 but a little practice will accomplish it. The entire circular space 

 called the field should be evenly 'lighted; there should be no 

 shadows nor faintness in the glow near the edge. Some writers 

 recommend that a piece of tissue paper shall be placed over the 

 stage-opening and the mirror manipulated until the light is 

 thrown exactly in its centre ; it is then removed and the light of 

 course passes through the objective and up the body tube. This 

 is a good plan if the reader lias trouble in seeing where the 

 reflection is thrown, but usually the light may be observed on the 

 front of the objective. The field can scarcely be illuminated while 

 the eye is at the eye-piece ; the illumination may then be com- 

 pleted, but not begun. The only plan is to use the paper on the 

 stage, or to observe when the front lens receives the light. Then 

 apply the eye and gently manipulate the mirror, trying to improve 

 jnatters ; but even now the best can not be obtained. This must 

 -wait until the slide is on the stage, when the body is carefully 

 traicked down and the focus obtained as previously directed. It 

 is possible that the field may then be evenly illuminated, but too 

 faintly to show the object properly, or oblique shadows may be 

 thrown across it, or only one little space] at the side may be bright 

 while all the rest is semi-obscure. This must be remedied by 

 wently moving the mirror, while eye is at'the ocular. When all 

 tthe circular region is lighted as well as seems possible, remove 

 the eye-piece and centre the illuminating beam by the method 

 suo-gested by Mr Edward Pennock|and described on a preceding 

 page. Then with the eye-piece again in position, the field should 

 p,ppear brightly lighted in every part. It will probably be too 

 bright and the observer must either rack down the condenser, if 

 he uses one, as he should, until the desirable softness of illumin- 

 ation is obtained, or the same result is to be worked for by rotat- 



