452 PREPARATION, MOUNTING, AND COLLECTION OF OBJECTS 



short bar with which the decentring wheel may be turned, forcing 

 the pin against the slide, pushing it as far out of centre as may be 

 desired. Another improvement is in making the end-pin a screw, 

 which may be turned down out of the way if desired. 



Mounting Plate and Water-Bath. Whenever heat has to be 

 applied either in the cementing of cells or in the mounting of 

 objects, it is desirable that the slide should not be exposed direct to 

 the flame, but that it should be laid upon a surface of regulated 

 temperature. As cementing with marine glue or hardened Canada 

 balsam requires a heat above that of boiling water, it must be 



FIG. 382. Apparatus for preparing mounting media, paraffin, &c., for imbedding 



by heat. 



supplied by a plate of metal ; and the Author's experience leads him 

 to recommend that this should be a piece of iron not less than six 

 inches square and half an inch thick, and that it should be 

 supported, not on legs of its own, but on the ring of a retort-stand, 

 so that by raising or lowering^ the ring any desired amount of heat 

 may be imparted to it by tne lamp or gas-flame beneath. The 

 advantage of a plate of this size and thickness consists in the 

 (jradational temperature which its different parts afford, and in the 

 slowness of its cooling when removed from the lamp. When many 

 cells are being cemented at once, it is convenient to have two such 

 plates, that one may be cooling while the other, is being heated. 



