Society of Glass Technology · [Sheffield] · leaf 648
this escape of air may be facilitated byinverting the two lenses and having the minor lens below themajor one. Since in bifocal lenses made in this manner the fieldof view of the minor lens is entirely free from the major lens, it ispossible to use tinted glass for the major lens and clear glass… … lenses, in which the rotating lens-holder is moved towards andfrom the grinding-wheel under the control of a templet, the lens-carrying frame is angularly adjustable, in order to grind the twosides of a V-shaped edge, about an axis which is always tangential 218 JOURNAL OF THE SOCIETY OF GLASS…
Glass
Internet Archive · Gerstein Library, University of Toronto · Public Domain Mark 1.0. Free to use for anything.
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