PREPARATION AND MOUNTING 81 



it a soaking in clean turpentine and mount in 

 Canada balsam on a 3x1 inch glass slip in the 

 ordinary manner. 



This method apphes to hard rocks. Rocks which 

 are friable, soft and loose in texture, such as coal, 

 need to be bound by some medium, lest they break 

 up in grinding. They may be prepared for grinding 

 as follows : Cut thin plates with a fine saw and soak 

 them for some hours in benzole. The benzole 

 must soak into the texture of the material. Then 

 soak in balsam and benzole until thoroughly pene- 

 trated by the balsam. Place the section on a 

 3x1 inch slip, and cover with balsam ; set aside in 

 a dust-proof place until the benzole has evaporated. 

 Then place the slip on the mounting-table, light the 

 spirit lamp, and bake until the balsam is thoroughly 

 hard. The section is now ready for grinding until 

 thin enough on a hone of water-of-Ayr stone. After 

 grinding, wash in water, dry, cover with balsam and 

 benzole, and place a cover-glass over all in the 

 usual way. It wiU be noticed that in this instance 

 the section is not removed from the glass slip after 

 once being attached thereto. 



11 



