A' remarkably hard diamond was once exhibited at th cFrcmli Academy of Sciences . It was a compound crystal of •the class known in France as “extreme derate,” and all attempts to polish it had been in vain. ft was kept on the polishing table for 100 days, with the wheel revolving at a speed of 2800 re volutions per minute. Calculation shows that the friction surface traversed by tTio facet in that time was 75,000 miles, or nearly three times the circumference gf the earth. Nevertheless, the stone, remained unpolished, ever’ after the pressure on it was increased to 401 b. The wheel was badly damaged, the diamond ploughing into it and scattering sparks in all directions
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Waipukurau Press, Volume 11, Issue 39, 12 August 1920, Page 4
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117Untitled Waipukurau Press, Volume 11, Issue 39, 12 August 1920, Page 4
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