THE MICROSCOPE. 29 



the fluid out at the sides of the cage. If the 

 water is thus allowed to overflow, it runs ovei 

 the glasses of the cage, and thus obscures vision. 

 An object or objects having been thus placed 

 in the cage, it is conveyed to the stage, and 

 placed in such a position that the ray of light 

 passing from the mirror to the object-glass may 

 pass through it. This having been done, the 

 observer must now 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 adjustment 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 

 mechanical stages. 



When objects not requiring the live-box or 

 animalcule - cage are to 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. (Fig. 8.) Some 

 transparent objects may be seen without any me- 

 dium, 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, so that 



