10 MICROSCOPY FOR BEGINNERS. 



formed of two lenses at the opposite ends of a short 

 tube inserted into the upper end of the body, the arm 

 supporting the body, the stage on which the object is 

 placed to be examined, the mirror to light the object, 

 a movable circular plate, or diaphragm, immediately be- 

 neath the stage, and the foot that supports the whole. 

 The addition of the objective, or magnify ing - glass, at 

 the lower end of the body, makes the stand a compound 

 microscope of the simplest form. The objective is so 

 named because it is near the object to be examined when 

 the microscope is in use, and the eye-piece is so called 

 because it is then near to the observer's eye. Without 

 both of these sets of lenses the instrument is useless. 



The arm and foot may be made of either brass or 

 iron, and there should be a joint between them so that 

 the upper parts of the instrument may be inclined. The 

 cheapest stands are made without this arrangement, and 

 they must therefore always be used in a vertical posi- 

 tion, the observer being compelled to hold his head and 

 body in a way that soon becomes very wearisome. An 

 iron arm and foot are quite as useful as if made of brass, 

 but no stand should be selected without the joint for in- 

 clination. Brass looks better, and is much more expen- 

 sive than neatly japanned iron, but is practically no 

 more useful. 



The body should be about ten inches long. In the 

 less expensive stands it is often made in two parts, the 

 upper tube sliding within the other, so that when it is 

 drawn out to its full extent the entire body will then be 



