MOUNTING OPAQUE OBJECTS. 



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these discs the objects may be mounted in the usual way, 

 A little practice will enable a person to make them easily, 

 and of a circular figure ; they may be also made of an oval 

 shape by spreading out the wax on the pin, being careful 

 that the thicker part of it occupies the centre of the pin, and 

 not one of the ends, otherwise irregular shapes, and not ovals, 

 will be the result. The ground upon which the object is to 

 be placed is necessarily shiny, but it can easily be made to 

 assume a dead black hue by scraping it with a knife. Discs 

 so made are very durable, and have a neat appearance. 



On Cylinders. — These may be made of cork, wax, or ivory, 

 of the shape represented by fig. 219 ; the pin may be passed 

 either through the long or the short axis 

 of the cylinder, so that an object may be 

 mounted on the ends of the latter, or on the 

 side of the former. Gutta percha, which is 

 now coming into use for lathe bands, and 

 may be obtained of nearly any size, can be 

 cut into lengths of half-an-inch or more, and 

 a pin heated to a temperature a little above 

 that of boiling water may be readily passed 

 through them, and when cold will be fixed 

 Fig. 219. very tightly. 



On Slides. — This is most easily done by 

 punching out from black paper little circles from the one- 

 fourth to one inch in diameter; these may be stuck either 

 with gum or paste upon the ordinary sized glass slide, as 

 shown by fig. 220 ; upon these black discs the objects may be 



Fig. 220. 



fixed with any of the cements before alluded to, in the same 

 manner as on those of cardboard or leather. They possess this 

 great advantage, that they may be arranged in a cabinet with 

 other objects, which cannot be done with those on the pins ; but 

 they are very liable to be injured materially by dust and dirt, and 

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