published by The Keystone, THE ORGAN OF THE JEWELRY AND OPTICAL TRADES, 19TH & Brown Sts., Philadelphia, U.S.A. THE OPTICIANS MANUAL VOL. I. By C. H. Brown, M. D. Graduate University of Pennsylvania; Professor of Optics and Refraction ; formerly Physician in Philadelphia Hospital; Member of… … The Opticians Manual, Vol. I., hasproved to be the most popular work onpractical refraction ever published. Theknowledge it contains has been moreeffective in building up the optical profes-sion than any other educational factor.A study of it is essential to an intelligentappreciation of Vol. II.,…
Clocks and watches
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