THE STUDY OF THE ROCKS 



little by acids. With such specimens the only course 

 open to the microscopist is to prepare sections. 



" The making of rock sections is certainly different 

 to the cutting of plant or animal sections. It is 

 a laborious business as the enthusiast will find to 

 his cost. The professional makers of rock sections 

 have special grindstones or lathes for the purpose 

 and, even so, the process is not rapid. The amateur 

 must needs do all his preparation by hand. The 

 requirements, in addition to the piece of rock of 

 which we require a section, are a small square of 

 plate glass, some Canada Balsam, emery powder of 

 various grades and an unlimited stock of patience. 

 If possible we choose a piece of rock with one side 

 as nearly as possible fiat; this is merely to save 

 labour; the piece of rock should be roughly about 

 half-an-inch square. As a start we rub the flattest 

 side in a mixture, practically a paste, of coarse 

 emery powder and water. As a matter of fact, we 



' may keep the piece of rock in our pocket and grind 

 it when occasion offers on a flat stone wall or on 

 any surface that will assist in producing a flat 

 surface. When we have ground our surface flat and 

 smooth, we finish it off with fine emery powder 

 and may then polish it with jeweller's rouge. So 

 much for the first side and, if we do not cry enough 

 at this period, we may proceed to the grinding of 

 the other side. Taking our slab of plate glass, we 

 fasten the polished side of our piece of rock to it 

 by means of Canada Balsam, then we may rest for 

 a few days while the Balsam sets. As soon as the 



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