Hall, Edwin Herbert, 1855-1938 · New York, H. Holt and company · leaf 163
omatic lenses. A large lens practically free from spherical and chromaticaberration is a marvel of skillful and patient work. Grlasssuitable for making a large lens of the best quality is verydifficult to procure, as a very slight flaw or unevenness ofquality may spoil a large block. The shaping… … REFRACTION OF LIGHT. 151 skillful and patient enough to do it become known through-out the world. For many years the largest and best lenses for greattelescopes have been made by Alvan Clark and his two sonsof Cambridge, Massachusetts; but now all of these famousmen are dead. The largest lenses…
Physics
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