THE MICROSCOPE. 13 



place his eye over the eye-piece, and use the screw 

 in the tube, and move the object-glass downwards 

 until he gets a clear view of objects moving in the 

 water. This is called focussing. The glass may 

 then be moved up or down, in order that the best 

 view of the object may be obtained. When the 

 object-glass is one of high power, the fine adjust- 

 ment, which is attached to most compound in- 

 struments, may be used for this purpose. When 

 the proper focus is obtained, the object may be 

 moved up or down, right or left, with the hand, 

 or by the aid of the screws which are employed 

 in the various forms of what are called movable 

 stages. 



When objects not requiring the live-box or ani- 

 malcule-cage are to be observed, they may be 

 transferred to the glass slide, by aid of a thin 

 slip of wood, or a porcupine-quill moistened at the 

 end, or by a pair of small forceps. Some trans- 

 parent objects may be seen without any medium, 

 but generally it is best to place them on the slide 

 with a drop or two of clean water, which may be 

 placed on it with a dipping-tube. When water is 

 used, it will generally be found best to cover the 

 object with a small piece of thin glass. Small 

 square pieces of thin glass are sold at all the 

 opticians' shops for this purpose. The object is 

 then placed under the object-glass as before. 



In order to render objects transparent, S that 

 they may be viewed by transmitted light, very 

 thin sections of them should be made. This may 

 be effected by means of a very sharp scalpel, or a 

 razor. When objects are too small to be held in 

 the hand to be cut, they may be placed between 

 two pieces of cork, and a section of them made at 

 the same time that the cork is cut through. 



Sometimes it is found desirable to unravel an 



