MICROSCOPIC OBJECTS. 145 



tools are ready, a number of glass slides may be bomid 

 together and ground on the tool with water and emery. 

 The chief care required is to grind uniformly on every 

 part of the surface of the tool. 



In some cases it is desirable to bevel the edges of the 

 slides. When this is required, it is necessary to attach 

 them to a block of wood, one side of which is bevelled 

 to the required angle. 



(5.) Polishing Slides. — Allien this is required, the po- 

 lishing may be effected by rubbing them on a flat tool 

 covered with either leather or silk. The surface of the 

 material on which the glass is to be polished must be im- 

 pregnated with putty-powder (oxide of tin and lead) or 

 the red oxide of u-on. Either of these is used, like the 

 emery, with water. It is necessary to remark, that prior 

 to the polishing the edges must be made perfectly 

 smooth by grinding with fine emery-powder. 



(6.) Mounting Transparent Objects between Glass Slides of 

 equal thickness. — An elegant method of mounting trans- 

 parent objects which do not require an object-glass of 

 short focus for their examination — as sections of recent 

 woods, entire mosses, &c. — is to place them between two 

 bevelled edge shdes of equal size, as shown in the figure. 



In this case the edges should be left rough from the 

 grain emery, as they thus take better hold of the cement 

 or seahng-wax with which the groove formed by the 



