CONSTRUCTION OF THE MICROSCOPE. 



83 



isms which act as fer- 

 ments. The general ar- 

 rangement of this instru- 

 ment is shown in Fig. 56. 

 On the table which forms 

 its base, there rests a box 

 containing a glass mirror 

 silvered on its upper sur- 

 face, which is placed at 

 such an angle as to reflect 

 the light-rays received 

 through the inverted Ob- 

 jective mounted on the 

 top of tbe box, into the 

 body fixed into its oblique 

 face. Over the objective 

 is placed the Stage, above 

 which again is the Mirror 

 for reflecting light down- 

 wards through the object 

 placed upon it. The 

 focal adjustment is made 

 in the first place by 

 means of a sliding tube 

 which carries the objec- 

 tive, and then by the 

 inicromet er-screw v, 

 which raises or lowers the 

 stage. The platform on 

 which the optical appar- 

 atus rests, can be moved 

 in rectangular directions 

 by the two milled-heads, 

 o, T; and is furnished 

 with two graduated scales, 

 by means of which it may 

 be brought with exact- 

 ness into any position pre- 

 viously recorded, so that 

 any point of the object 

 may be immediately re- 

 found an arrangement 

 of special value in cultiva- 

 t i o n - experiments. On 

 the stage is a circular 

 glass cell, c, for holding 

 the fluid to be examined; 

 in the bottom of this in 

 a n aperture, which i s 

 closed by a piece of thin 

 cover-glass well cemented 

 round its edges, thus al- 

 lowing the use of high 

 magnifying powers hav- 



Swift's Portable Binocular, as set up for use. 

 5 JB. 



Swift's Portable Binocular, as packed in case. 



