ANIMALCULE-CAGE. 195 



all round the object-plate, so that the fluid and animalcules 

 in it were retained at the top of the object-plate by capil- 

 lary attraction. The cover is made in the usual way to 

 slide up and down over the object-plate. The plate of 

 brass to which the tube supporting the tablet and cover 

 is attached, is of a circular form, slightly flattened on its 

 two opposite sides for convenience of package. The in- 



Fig. 121. Varleifs Aiiimakule-cage. 



strament is seen in elevation and in section in fig. 121 

 A, B, in both figures, is a flat plate of brass to which the 

 short tube carrying the object-plate or tablet is fixed; 

 d, the piece of brass into which the tablet c is fastened ; 

 b, the. tubular part of the cover, into the rim of which 

 the thin plate of glass a is cemented. 



Compressorium. The purpose of this instrument is to 

 apply a gradual pressure to objects whose structure can 

 only be made out when they are pressed or thinned out 

 by extension. The general plan of the compressorium is 

 shown in fig 122 



Ross's Compressorium consists of a stout plate of brass 

 A, about three inches long, having in its centre a piece of 

 glass like the bottom of a live-box. This piece of glass 

 is set in a frame B, which slides in and out so that it can 

 be removed for the convenience of preparing any object 

 upon it, under water if desirable. The upper moveable 

 part D is attached to a screw-motion at (7; and at one end 

 of the brass-plate A, which forms the bed of the instru- 

 ment, is an upright piece of brass (7, grooved so as to 

 o2 



