ON MOUNTING OBJECTS. 



79 



after maceration, which facilitates removal of the object from time to 

 time for the purpose of examining it. It is made of two stout strips 

 of whalebone three or four inches in length, held together at each end 

 with square pieces of brass ; these may be moved at pleasure towards 

 the centre, and thus made to exert considerable pressure upon the 

 pieces of glass and the object, which are placed crossways between the 

 strips of whalebone. 



For the purpose of more effectually removing bubbles of air from 

 the cells before cementing them down, the small air-pump, fig. 64, 

 will be found serviceable. This can be purchased of Baker, Holborn, 



nTmniirrnrrmT 



fig. 64. 



at a moderate price. The mode of using it, is simply to place the 

 object, after having warmed it and covered it with the thin glass, under 

 the bell-glass c ; then, by drawing up and pushing down the handle B, 

 pump out the air until the whole of the small bubbles are withdrawn 

 from around the object to be secured and preserved. By turning the 

 small screw at D, you will let in sufficient air to remove the bell-glass ; 

 or allow your object to remain under it for several hours until the 

 cement around the edge of the glass-cover becomes perfectly dried and 

 secure, when exposure to the external air will no longer affect it. It 

 will be also found useful in withdrawing the air from the cells of woods 

 or limbs of insects. The pump itself, A, when unscrewed, can be used 

 as an injecting-syringe for fine anatomical injections. 



