Side-lights on astronomy and kindred fields of popular science; essays and addresses (1906)
Newcomb, Simon, 1835-1909 · New York Harper · leaf 99
irring rod,which become mixed in with the glass in consequenceof the intense heat to which all are subjected. Theseveins must, so far as possible, be ground or chippedout with the greatest care. The glass is then melted 79 SIDE-LIGHTS ON ASTRONOMY again, pressed into a flat disk, and once more put… … THE GLASS DISK problem now is to remove these by cutting and grind-ing without either breaking the glass in two or cuttinga hole through it. If the parts of the glass are onceseparated, they can never be joined without producinga bad scar at the point of junction. So long, how-ever, as the surface…
Astronomy
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