Accessory Apparatus 



119 



Rousselet's Compressor. — Mr. Eousselet, the designer of 

 tlie live-cage previously mentioned, is also the originator of 

 the most efficient compressor at present obtainable. It is 

 shown in Fig. 49. The upper arm has cemented to its 



Fig. 48.— Eousselet's Live-cage. 



under side a portion of a circle of thin cover-glass, which 

 enables high-power objectives to be employed, and the disc 

 of glass in the base-plate is not 

 too thick to prevent the em- 

 ployment of condensers of large 

 aperture. The compression is 

 quite parallel in action, being 

 effected by turning a milled 

 head at the top of a drum 



containing a spring, which causes the upper plate to rise 

 when the milled head is released. The cut-off top of the 

 cover-glass permits of different media being inserted while 

 the specimen is under examination, and the arm can be 

 turned aside when desired for cleaning, etc. 



Fig. 49. — Eousselet's Com- 



PllESSOlllUM. 



