Roch Section ('uttiiKj A/i/xi rafas. 75 



fXrinding and polisliiu^^ of small luinri-al and olher sjieciiuens. 



This is an addition to its varied usefulness in the workroom 

 generally. 



4. — Method of Slicing, Grinding and Mounting 

 Rock Sections. 



It is only by adopting and }»ursuiug a methodical and co- 

 ordinated series of operations that the full value of a machine 

 similar to the one just outlined is fully secured. To this end 

 I have adopted a systeu) of working, the main features of which 

 are embodied in the following brief sumnuiry of its salient 

 points : — 



A. ('/i(/r(///i(/ thf Slicrrs, Etc. This is invariably done with 

 diamond powder, which it pays to crush, and sift from time to 

 time during the operation. The sifting is easily done with the 

 aid of several bits of glass tube about lin. long and fin. wide, 

 to one end of which, aftei' grinding level, a bit of very tine 

 bolting silk has l)een cemented. A slicer charged with pro- 

 jierly graded diamond powder cuts faster and cuts longer than 

 would be the case if the diamond were only ground to an 

 almost impalpable powder in oil, as is frequently done : the 

 former method is more efi'ective as well as more economical. 



Every slicer should l)e niacle to run " de.id " true, and should 

 be maintained in that condition. The greater the speed at 

 which it is run, the more important it becomes that it should 

 run trvdy. A slicer is always ineii'ective in pro]>ortion to its 

 eccentricity. Too often the slicer is -made to cut as long as it 

 will cut ; this is unsound, both in theory and practice. 



With regard to charging a slicer, T find a chilled steel roller 

 by far the most eli'ective instrument for this pur])ose. It is 

 better than any glass or ag;ite implement : and, if ])roperly 

 made, is ahnost everlasting. 



I have tried notching the slicers and charging the notches ; 

 it takes a long time to do this well — and it must be well done, 

 or not at all. 1 was certainly rewarded with a slicer which 

 cut well for a. long time. T'sually, however, I find a slicer 

 charsred in the ordinary wav, that is bv picssure of the diamond 



