Side-lights on astronomy and kindred fields of popular science; essays and addresses (1906)
Newcomb, Simon, 1835-1909 · New York Harper · leaf 100
months of labor he cannot perfectly clear his glassof the noxious veins, and he has to break it up intosmaller pieces. When he finally succeeds, the diskhas the form of a thin grindstone two feet or upwardin diameter, according to the size of the telescope tobe made, and from two to three inches in… … THE OPTICIAN S TOOL must be ground in a saucer-shaped tool of correspond-ing form. It is impossible to make a tool perfectlyspherical in the first place, but success may be se-cured on the geometrical principle that two surfaces 81 SIDE-LIGHTS ON ASTRONOMY cannot fit each other in all positions…
Astronomy
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