Use of Carborundum for Ruling Test Plates

Abstract

THE communication from Mr. A. Mallock in NATURE of September 1, p. 10, reminds me of the marked success that I have had in the use of fine carborundum points for scratching on glass. Some years ago, when confronted with the task of preparing small oscillograph mirrors from microscope cover-glasses, I found that a small fragment of carborundum crystal tied in the split end of a match or forced into a piece of soft rubber for a handle made an excellent glass-cutter. The scratches were so fine and clean-cut that the glass could easily be broken into very narrow strips.