CH. /] MICROSCOPE AND ACCESSORIES 27 



(frontispiece) so that there may be plenty of room between its lower 

 end and the stage. Grasp the objective lightly near its lower end with 

 two fingers of the left hand, and hold it against the nut at the lower 

 end of the tube. With two fingers of the right hand take hold of the 

 milled ring near the back or upper end of the objective and screw it 

 into the tube of the microscope. Reverse this operation for removing 

 the objective. By following this method the danger of dropping the 

 objective will be avoided. 



48. Putting an Ocular in Position and Removing it. Ele- 

 vate the body of the microscope with the coarse adjustment so that the 

 objective will be 2 cm. or more from the object grasp the ocular by 

 the milled ring next the eye-lens (Fig. 21), and the coarse adjustment 

 or the tube of the microscope and gently force the ocular into position. 

 In removing the ocular, reverse the operation. If the above precau- 

 tions are not taken, and the oculars fit snugly, there is danger in in- 

 serting them of forcing the tube of the microscope downward and the 

 objective upon the object. 



49. Putting an Object under the Microscope. This is so 

 placing an object under the simple microscope, or on the stage of the 

 compound microscope, that it will be in the field of view when the 

 microscope is in focus ( 50). 



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

 microscope. The difficulty increases, however, with the power of the 

 microscope and the smallness of the object. It is usually necessary to 

 move the object in various directions while looking into the micro- 

 scope, in order to get it into the field. Time is usually saved by get- 

 ting the object in the center of the field with a low objective before 

 putting the high objective in position. This is greatly facilitated by 

 using a nose-piece, or revolver. (See Figs. 36-363, and the pictures of 

 microscopes, Ch. II.) 



FIG. 36. Triple nose-piece or revol- FIG. 363. Triple nose-piece or re- 



ver for quickly changing objectives. ( The volver for quickly changing objectives. 

 Spencer Lens Co. ) ( The Bausch & Lomb Optical Co. ) 



