TOOLS AND METHODS OF WORK 



33 



position by means of the wire "spring-clip" (Fig. i8 B), until the slide 

 is baked, or has set hard by the evaporation of the benzol. In 

 mounting solid specimens on cavity slips, the cavity must first be filled 

 with balsam, the specimen placed in this, and then a cover slip, whether 

 round or oval, one size larger than the cavity is placed in position. In 

 this case the spring-clip must be applied with only just sufficient 

 pressure to keep the cover in position during the drying operation, or 



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f /o 



Fig. 19. — Types of 3in. by lin. slips, used for mounting microscopical objects. 

 A. Plain slip. 1-5. Round cavity slips. 6-1 1. Oval cavity slips. 



there is a danger of the cover being depressed, by which means some 

 of the balsam would be squeezed out, and when the clip was removed 

 the cover would again spring up, causing suction thereby and 

 consequent air-bubbles to find their way into the cavity. 



When it is required to mount large entire specimens in fluid and 

 the ordinary cavity-slip is not suitable to this requirement, a cell should 

 be built up round the cavity with tin rings. 



