The Microscope Unpacked. 15 



powerful magnifier is still attached to the tube, and 

 getting it into the centre of the field, take off the 

 object-glass of low power and substitute the higher 

 one. Look in all is hazy, because the increased 

 power requires the tube to be lowered. But lower it 

 carefully, or you may presently find your object-glass 

 and slide meet with a crash, resulting in the breakage 

 of one or both. It is well to do this screwing- down 

 with the eye removed from the tube, and steadily 

 fixed on the object itself; look edgewise, and screw 

 downward till the object-glass and object nearly 

 touch, then place your eye to the eye-glass, slowly 

 reverse the movement of your hand, and the object 

 will start into clearness when at the proper dis- 

 tance ; and if there is an additional screw for what is 

 called the " fine adjustment," you can perhaps gain 

 further exactness in the focus. 



With a little practice you will soon estimate the 

 proper distance for each object-glass; and you will 

 also find it tolerably easy to find the object, even 

 without first getting it to the centre of the field with 

 the help of a lower power ; you may move the slide 

 somewhat rapidly about with your hands till the 

 object glances across the field, then lay it on the 

 ledge, reverse the motion which inadvertently whisked 

 it away, and you will soon see it coming back into the 

 field of view. 



" Which eye shall I shut ?" is not an unfrequent 

 question of persons to whom a microscope is shown. 

 Neither, is the answer in which all practised observers 

 seem to agree. Keep open the unemployed eye, and 



