OF THE MICROSCOPE. 25 



eye-piece and the objective. Stands are frequently sold .separ- 

 ately, or furnished with eye-pieces only the purchaser making 

 such a selection of objectives and other accessories, as may best 

 suit his special needs. 



The Base or Foot is that part which supports the rest of the 

 stand. 



The Body is the tube to which the eye-piece and objectives 

 are attached. 



A Draw-tube is a secondary body which receives the eye-piece, 

 and slides within the main body like the draw of a telescope. 

 It enables us to increase the distance between the eye-piece and 

 the objective, and thus to change the magnifying power, as 

 explained in a previous paragraph. 



A Collar is a short tube through which either the body, the 

 draw-tube, or the eye-piece slides. 



The Arm is that part which carries the body. 



The Stage is the plate upon which the object is placed for 

 examination. 



Clips are springs attached to the stage for the purpose of 

 holding in place the glass slide or plate carrying the object. 



A Sub-stage is furnished with some instruments. It is used 

 for holding and centering various means of illumination. No 

 sub-stage is shown in the diagram, Fig. 1. The sub-stage, with 

 its centering arrangements, is shown very clearly in the Ross 

 model, Plate I. 



Sub-stage Ring. Instead of being provided with a sub-stage, 

 many cheap microscopes are furnished with what is known as 

 a sub-stage ring or tube. This serves to receive the polarizer, 

 paraboloid, etc. 



The Object-Glass or Objective is the lens or lenses which are 

 placed next the object. The term Object-glass is sometimes 

 applied to the glass plate or slide upon which the object is 

 placed, but this use of the word is entirely wrong, and tends to 

 produce con fusion. 



The Society Screw is a screw of a certain standard size for con- 

 necting the objective to the body. In microscopes furnished 

 with a screw of the Society's standard, the objectives of any 

 American or English maker may be used. The makers on the 

 continent of Europe have now very generally adopted the So- 

 ciety Screw. In this country the Society Screw has been uni- 

 versally adopted, but as it has been foiind too small for low- 

 power objectives of wide angle, another screw, named the 



