12 THE STRUCTURE OF 



use of the Microscope under ordinary circum- 

 stances. The Microscope may be either used by 

 the light of the sun in the daytime, or at night 

 by some form of artificial light. It is best used by 

 daylight, as artificial light is more likely to tire the 

 eyes. 



Having determined to work by daylight, some 

 spot should be selected near a window, out of the 

 direct light of the sun, in which to place a small, 

 firm, steady table. On this the Microscope should 

 be placed, and the object-glass should be screwed on 

 to the tube. The mirror should be then adjusted so 

 as to throw a bright ray of light on to the object- 

 glass. The eye-piece having been previously placed 

 at the top of the tube, the Microscope is now ready 

 to receive a transparent object. If the object to 

 be examined is an animalcule, it may be conveyed 

 to the animalcule-cage by means of a glass tube, 

 which should be dipped into the water where the 

 object is contained, with the finger covered over 

 the upper orifice, so that no air can escape. By 

 taking the finger off when the tube is in the water, 

 the fluid will rush into the tube, and with it the 

 object to be examined. The finger is again applied 

 to the top of the tube, and the fluid obtained con- 

 veyed to the animalcule-cage : only such a quantity 

 of the water should be allowed to fall out of the 

 tube on to the cage as will enable the observer to 

 put on the cover of the cage without pressing the 

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

 thus allowed to overflow, it runs over the glasses 

 of the cage, and thus obscures the 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 



