LESSON I. 



THE USE OF THE MICROSCOPE. 



1. Examine the microscope. It has probably two 

 eye-pieces or oculars, No. 2 and No. 4 1 , and two object- 

 glasses or objectives frd inch and ^th inch 2 . 



The tube which carries the lenses is in some micro- 

 scopes moved towards or away from the stage by a rack 

 and pinion, in others simply by twisting it up or down 

 in a second tube. In the latter case see that the 

 microscope tube twists easily ; if it does not, clean the 

 tube thoroughly. When the microscope tube is moved 

 in this way, the coarse adjustment is said to be used. 



The tube can also be moved up or down by turning 

 a milled head at the top of the pillar of the microscope. 

 Turn the milled head, and note that turning it in the 

 direction of movement of the hands of a watch lowers 

 the microscope tube, and turning it in the contrary 

 direction raises the tube. When the microscope tube 



1 Eye-pieces of the same magnifying power are differently named 

 by different makers, and some name them A, B, C, etc. 



2 In Zeiss' microscope, objectives A and D correspond to the 

 gth and th inch respectively. 



