^ 





JOURNAL 



OF THE 



ROYAL MICROSCOPICAL SOCIETY. 



JUNE, 1905. 



TRANSACTIONS OF THE SOCIETY. 



Ill — Micro-Metallography with Practical Demonstration. 

 By J. E. Stead, F.K.S. 



{Bead February 15th, 1905.) 



As metals are opaque, it is impossible to deal with them as the 

 mineralogist deals with his rocks and minerals. Therefore, the 

 metallographer is obliged to depend upon what is revealed upon 

 then polished surfaces. On this account it is not necessary to 

 have specimens of any particular shape, size or thickness. The 

 only thing absolutely essential is that one surface is perfectly flat, 

 and is polished so as to have a mirror-like appearance, free from 

 scratches. 



It was Dr. Sorby, of Sheffield, who first elaborated a system for 

 the examination of the micro-constituents of Iron and Steel. His 

 methods are so well known that it is scarcely necessary to give 

 them here in detail. It is sufficient to state that the metals were 

 polished by hand on a series of emery papers diminishing in coarse- 

 ness, and finished upon rouged parchment. 



Polishing by hand takes a long time, and although the work 

 when properly finished is perfect, it has been found a very great 

 convenience to expedite the process by means of quick running 

 discs and grinding appliances worked by electrical or other power. 



Professor Martens polished on beds of pitch containing grinding 

 powders mechanically suspended, which were placed on the head of 

 a wheel running horizontally. A series of many specimens were 

 fixed with cement to a holder, which was caused to traverse back- 

 ward and forward across the polishing surface. 



Osmond proceeds by first grinding on emery papers by hand, 

 roughly polishing on rouged cloth, and then on a wheel covered 



June 21st, 1005 U 



