ZOOLOGY AND BOTANY^ MICROSCOPY, ETC. 



351 



strong screws r, and are connected by the centre bar z, wHcli is let 

 into them by a mortice and held by the pins _p. The clutches are 

 opened for the reception of the glass slip by placing a finger of the 



Fig. 90. 



Upper Side 



right hand against the milled end of the head-block at c (or c'), and 

 pressing the end of the lever-bar with the thumb at d (or d'). The 

 grasping force of the clutches is secured through a spiral spring s 



Fig. 91. 



Lower JSide 



(figs. 89 and 91), coiled around the head of the spindle, as shown in 

 the figures. 



The whole rests on disks of rubber, so that it will neither slide 

 about nor mar any surface on which it may be used. 



