COMPOUND MICROSCOPE. 



613 



eclairage, through which the light reflected from the mirror passes. The am- 

 plification by means of an eye-piece in the compound microscope enables us 

 to use an object-glass of a lower power than would otherwise be necessary. 

 This kind of microscope, when well constructed, gives a flat and colourless 

 picture of the object, with clearness of definition. The observer can use it for 

 a length of time with less fatigue than when employing the simple microscope. 



1195. In examining vegetable structures, an instrument magnifying 150 to 

 200 diameters is usually sufficient; but in some instances higher powers are 

 required. Achromatic object-lenses of 1^, f , and of an inch, are recommended 

 as the most essential; and two eye-pieces should be provided, one of about 

 1^ and the other of 2 inches in length. The instrument should have both a 

 coarse and a fine adjustment ; and it is of importance that it should be made 

 to incline at an angle, or to stand horizontally. A moveable stage is also use- 

 ful, so that the different parts of the object may be viewed without being 

 touched by the ringers, and a spring-holder to fix the objects on the stage. 



[The following figure (829 ) represents 

 an achromatic microscope of modern con- 

 struction. It consists of a massive cir- 

 cular foot ; jointed pillar to admit of the 

 instrument beingused either horizontally, 

 vertically, or at any intermediate angle ; 

 rack-workadjustment,withslidingstage; 

 Huyghenian eye piece ; set of three ach- 

 romatic object glasses, single lens and 

 adapter, concave mirror, stageand spring 

 forceps, animalcula? box, glass sliders 

 for receiving objects to be examined, 

 and pieces of microscopic glass for cover- 

 ing objects, with objects mounted in 

 Canada balsam on sliders. 



DIRECTIONS. The spot best adapted 

 for microscopic observations is one free 

 from tremor, where a good light, either 

 from a white cloud, or Argand lamp, 

 may be obtained. The mirror, A, and 

 optical parts of the microscope are to be 

 rendered free from dust by the careful 

 use of a piece of chamois leather, or 

 camel's-hair pencil; the foot, g, is to 

 be screwed to the pillar, /, and the eye- 

 piece, o, having been slid into one end 

 of the body, a, and the object glass, i, 

 or _/, being screwed into the other end ; 

 the body is then to be firmly screwed 

 into the arm, c, and the compound body 

 inclined so as to bring the eye-piece, o, in such a position as to be opposite th 

 eye of the observer when sitting in an easy posture. The adjustment of the 

 light is the next step, and this is easily effected by turning the mirror, ft, until 

 the light reflected by it passes through the hole in the centre of the stage, e, and 

 the maximum amount will be obtained by now looking through the instrument, 

 and slightly varying the position of the mirror, until the whole field of view is 



