150 MICROSCOPIC OBJECTS. 



for very minute objects, which is preferred by some 

 microscopists : here the pin is encased with blackened 

 wax or cement, or it may consist of small cork cylinders. 

 The third plan of mounting shown in the drawing consists 

 of cylinders of cork or felt. They are punched out of a 

 piece of either of those materials, whose thickness is 

 equal to the length of the required cylinder, and having 

 a common pin passed through them. They must be 

 blackened with common lacquer and lamp-black, holding 

 them over a candle to dry. Sometimes these cyhnders 

 are made of ivory : in such case the inside should be 

 turned hollow hke a small box, and the pin, as before, 

 running through the middle, is to be the support of the 

 object instead of the surface, as in the cork cylinders. 

 The ivory is then to be dyed black, and the inner surface 

 made as sombre as possible. This plan enables the 

 observer to see the dehcate structure of an object more 

 distinctly ; indeed it is the only method by which we can 

 develope the structure of some objects by reflected light, 

 such as the minute sponge-like glands over the foot of 

 the common fly. Remember, that the darker the object 

 the more black and sombre must be the mounting. In 

 such cases the reflected rays of light from the object are 

 so few that reflections from other bodies would entirely 

 drown them. This it is necessary to mention, as some 

 persons have thoughtlessly mounted their objects on the 

 white ivory. The glare and fog produced by this mistake 

 are sufacient to injure the vision of the most perfect 

 instrument. 



