4:, THE MICROSCOPE. 



A. Base of the instrument and part that forms its entire sup- 

 port. This may be in the form of a horse-shoe or a tripod, support- 

 ing at three points. This condition is desirable, as greater solidity 

 is thereby given to the instrument. 



B. Pillar. This is the upright support from the base and 

 usually has a joint at the top, by means of which the instrument 

 may be inclined. 



C. Arm. This carries all of the remaining parts of the 

 instrument. 



D. Body. This is the tube holding the optical parts of the 

 instrument that are above the stage. The raising and lowering of 

 these is controlled either by a gearing or by friction of the outer 

 stationary part with the inner movable one. 



E. Nose-Piece. A small revolving part fastened to the 

 lower end of the body and forming an attachment for the objectives. 



F. Objective This is the lower of the lens combinations 

 above the stage and is usually screwed into the nose-piece. Most 

 microscope makers use a uniform size of thread and this is known 

 as the society screw. The function of the objective is to form an 

 image of the object. 



G. Ocular The part holding the upper combination of 

 lenses, and fitting into the upper end of the body. The function 

 of the ocular is to magnify the image produced by the objective. 



H. Draw-Tube This forms the inner part of the body and 

 moves in an outer sheath. The length of the body may be varied 

 by the adjustment of the tube in its collar. 



I. Collar. A ring fastened to the upper end of the body and 

 forming a sleeve for the draw-tube. 



J. Course Adjustment. This is used for raising and lowering 

 the body. It is provided with two large milled heads (K), which 

 revolve a pinion that acts upon a rack, and controls the working 

 of the adjustment. 



L. Fine Adjustment. Used to raise or lower the body 

 slowly through short distances, in this way obtaining the exact 

 focus. It consists of a milled head with a screw that acts upon the 

 body of the instrument. 



M. Stage This is firmly attached to the pillar and is for 

 the support of the object during examination. Sometimes a 



