Ch. I] 



FIELD OF THE MICROSCOPE 



29 



tion. In removing the ocular, reverse the operation. If the above 

 precautions are not taken, and the oculars fit snugly, there is danger 

 in inserting them of forc- 

 ing the tube of the micro- 

 scope downward and the 

 objective upon the object. 

 § 46. Putting an object 

 under the microscope. — 

 This is so placing an object 

 under the simple micro- 

 scope, or on the stage of 

 the compound microscope, 

 that it will be in the field 

 of view when the micro- 

 scope is in focus (§ 47, 69, 



fig. 63). 



With low powers, it is not difficult to get an object under the micro- 

 scope. The difficulty increases, however, with the power of the micro- 

 scope, and the smallness of the 

 object. It is usually necessary 

 m t to move the object in various 

 directions while looking into the 

 microscope, in order to get it 



into the field. Time is usually 

 » » ... 



saved by getting the object in 



the center of the field with a 



low objective before putting the 



Fig. 28. Quadruple Nose-piece with the 

 Four Objectives in Place. 



16 



8 



high objective in position. This 



Microscopic Field with and j s greatly facilitated by using a 

 without Oculars. . , ,_ , 



nose-piece, or revolver (fig. 20- 



28). 



§ 47. Field or field of view 

 of a microscope. — This is the 

 area visible through a micro- 

 scope when it is in focus. When 

 properly lighted and there is no 



A The field of the 2. 4. 8. 16 and 32 

 mm. objectives without an ocular. 



B Field of the same objectives with a 

 Sx ocular. 



C Field of the same objectives with a 

 iox ocular. 



32, 16, 8, 4, 2 Equivalent focus of 

 the different objectives whose fields are 

 shown. 



