PREPARATION AND MOUNTING 69 



it that a narrow margin of the ring extends beyond 

 it. For very thin objects only one ring will be 

 necessary, and as soon as it is made the slip should 

 be set aside to dry in a dust-proof place. If thicker 

 objects have to be provided for, the cell can be 

 deepened by superimposing two or three more rings 

 of gold-size, but each layer must be allowed to dry 

 before another is added. 



Suppose we desire to mount a portion of a butter- 

 fly's wing. Taking a prepared cell of requisite 

 depth, we cut the object so that it will fit inside the 

 cell without moving. If cut square it can be held 

 in position by the corners where they touch the 

 ring. Then, object in place, we put the slide on 

 the turntable and run a thin layer of gold-size on 

 the surface of the cell, and set it aside to dry until 

 it becomes " tacky." When this condition is 

 reached, we clean a cover-circle, lay it gently and 

 evenly on the cell, and, using gentle pressure, see 

 that it adheres all round its edge. We seal and 

 finish the cell with a ring of Club Black enamel, 

 label the slide, and, when the enamel is set, put it 

 away until required for use. 



The worker must take care that the object, the 

 glass shp, and the cover-glass, are perfectly dry, and 

 even that the gold-size is hard, with the exception of 

 the tacky top layer, before the object is enclosed. 

 Failing this, the slide wiU be ruined. Cover slips 

 should be lifted with the forceps and passed two or 

 three times through the flame of the spirit lamp in 

 order that moisture may be driven away, and if 

 there is suspicion of moisture on the slip or in the 

 object, they ought to be dried with gentle warmth. 



