162 HOW TO SEE WITH THE MICROSCOPE. 



thus ^ot light enough, next proceed to find your object 

 and to focus the same, and if the approximate correc- 

 tion for the objective is known it will be well now to 

 apply it. 



Next, we proceed to attempt the proper display of 

 the object, Seize the lamp with the right hand, turn 

 the edge of the flame edgewise to the illuminator, and 

 move the lamp bodily, sliding it on the table in all 

 directions, to the right, to the left, towards the stand 

 away from it. If, while thus manipulating the lamp, 

 the field should be lighted with a succession of colors, 

 blue, red, green, etc., you may be pretty sure that things 

 are working well. Making sure, now, that the edge of 

 the lamp flame is turned to the " reflex," and still grasp- 

 ing the lamp with the right hand, and the fine adjust- 

 ment with the left, try the effect of very small move- 

 ments of the lamp ; these will be followed with a change 

 of color in the field. Supposing, now, that the distance 

 of the lamp from the stand is just right. We will find 

 that by pushing it horizontally and parallel to the front 

 edge of the stage, towards the left, we shall shortly have 

 a blue field, while with a little further shove in the 

 same direction we lose our illumination. Now it is in 

 such positions, and just at the point where the illumina- 

 tion begins to decrease, that I get the strongest resolu- 

 tions of severe tests. If we now retrace the path of the 

 lamp, carrying the same towards the right, the field will 

 become tinged with red, and by pushing the lamp still 

 farther thereto this will deepen, while another move- 

 ment of the lamp in the same direction will cause the 



