Society of Glass Technology · [Sheffield] · leaf 559
he mark, formed bythe three lenses, from the second focal plane of the positive system;s directly proportional to the vertex power to be measured. Thisdistance is measured by focusing the eyepiece. J. A. Tomkins (Optician, 1921, 61, 126) offered another explana-tion of the design of the instrument.… … Fig. 114. ILLUMINATION AND ILLUMINATING WARE. 129 VI.—Illumination and Illuminating Ware. 233. Lighting Glass. E. Y. Davidson {National GlassBudget, 1921, 37, No. 13, 24).—In commercial lighting, examples ofsmall enclosing globes surrounding huge large capacity lamps werein evidence in any business…
Glass
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