The dictionary of photography for the amateur and professional photographer (1897)
Wall, E. J. (Edward John), 1860-1928, Bolas, Thomas · London : Hazell, Watson & Viney · leaf 441
egative in position, a screw may be driven through one end of the printing frame, and the point of the screw cut off ; a groove cut in it in which to fit the negative. To the back affix three or four small tongues of metal pierced with holes, which holes may drop over pins driven into the sides of… … the principal axis, a c a' (fig. 88) ; then from the centres of curvature draw two radii, ab and a'b', parallel to one another, 43i
Photography
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