THE MICROSCOPE, 21 



proper distance from the object-glass, or a drop 

 of water may be placed on the slide, and a piece 

 of thinner glass placed over the object. This is 

 the most convenient arrangement, as you may 

 then tilt your Microscope without the slide or 

 object falling off. 



Objects, when placed under the Microscope, are 

 of t\vo kinds either transparent or opaque. When 

 they are opaque, they may either be placed upon 

 the slips of glass, or put between a small pair of 

 forceps (tig. 8), which are fixed to the stage of the 

 Microscope, and the light of a window or lamp 

 allowed to fall upon them. This is not, however, 

 sufficient, generally, to examine things with great 

 accuracy ; and an instrument called a condenser 

 (tig. 9) is provided for this purpose. It consists 

 merely of a large lens, which is sometimes fixed to 

 the stage, or has a separate stand. Its object is to 

 allow a concentrated ray of light to be thrown on 

 the opaque object whilst under the object-glass of 

 the Microscope. This is called viewing objects by 

 reflected light. 



Transparent objects, *>n the other hand, are 

 viewed by transmitted light, reflected from the 

 plane or concave surface of the mirror beneath the 

 stage. The object of this mirror, which is called 

 the re/lector, is to caUh the rays of light and con- 

 centrate them on the object under the Microscope^ 

 The rays of light thus pass through the object, and 

 its parts are sesii much more clearly. 



Another convenient piece of apparatus is an 

 animalcule cage. This consists of a little brass box, 

 inverted, to the bottom of which is attached a 

 piece of glass. Over this, again, is placed a lid 

 or cover, with a glass top. The cover can be made 

 to press on the glass beneath, and an object being 

 placed between the two glasses, can be submitted 



