Cyclopedia of architecture, carpentry, and building : a general reference work ... (1907)
American School of Correspondence · Chicago : American Technical Society · leaf 419
M (A KQ 0. S HXO o QO XH u£ ooo ELECTRIC LIGHTTXG 65 and prisms are arranged so that they can be reversed readily andtwo readings should ahvays be taken to compensate for any ine-qualiti3s in the sides of the screen and the reflecting surfaces, a … Fig. 55. mean of the two readings serving as the true reading. This form of screen is used when especially accurate comparisons are required. Fig. 55 shows a complete photometer with a Lummer-Brod- hun screen, while Figr. 56 shows a Bunsen Screen and sigrht box. 347 66 ELECTKIC LiGfiTIXG In Fig.…
Architecture · Building · Carpentry
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