102 MICROSCOPIC ILLUSTRATIONS. 



ployed in the microscope without reference being had to 

 any of the rest. By this means, persons engaged in parti- 

 cular investigations may easily judge of the peculiar appa- 

 ratus which is suited for them, and select accordingly. 



SECT. 1. Candle-holder, Shade, and Condenser for the 

 Microscope. The first addition to the mechanical portion 

 of a microscope we may consider to be the arm, Jc, repre- 

 sented at fig. 21, for carrying a candle or lamp, to 

 supply the requisite illumination. Those persons who 

 are in the habit of using an artificial light for the micro- 

 scope, are fully aware of the difficulties there are in con- 

 ducting their observations satisfactorily with it. Upon 

 all accounts, it is advisable that the candle or lamp- 

 holder should be attached to the stem of the microscope ; 

 for by this arrangement the light may be easily kept at 

 the required elevation, and the inconvenience arising 

 from the foot of the candlestick coming in contact with 

 the stand of the instrument, will be wholly avoided. 

 Besides, you will not experience the annoyance of being 

 continually obliged to alter the direction of the light, 

 through unconsciously moving about the microscope. 



Having given in the " Micrographia," page 219, a 

 description of the above-mentioned apparatus, together 

 with the shade, and shewn it by several engravings, in 

 the following pages, at the positions, k, 7, it is unneces- 

 sary for me to remark further upon it here. I may men- 

 tion, however, that the same rod which is used for the 

 purpose of regulating the illuminations, is made to 



