Howe, Herbert A. (Herbert Alonzo), 1858-1926 · Meadville, Penna., Flood and Vincent · leaf 141
ntity of light, and theo-retically injure the perfection of the image of an objectseen through the lens. When a careful test is made striae, or veins, may befound in the in-terior of the lens :should these benumerous or pro-nounced the lensmust be rejected. The glass mayhave passedthrough all… … F* —The Lump Cut Down Still More. the glass may A Great Telescope. 135 cloth, in some place where there is suitable light, andexamined by a Nicols prism. If a pronounced darkcross is seen in the glass, the internal strain is too great,and the glass must not be used for a telescope. The…
Astronomy
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