. The Bell System technical journal . s (hours long) again give a simple, strong, andreliable figure. 28 BELL SYSTEM TECHNICAL JOURNAL ample, CT slabs are to be examined the tiltable mounting-table is clampedin the 38° position, and the slab placed crosswise on the table (X-axis normalto line of sight, and beveled edge as shown). Upon moving the viewingscreen to position 1, only lamp 1 is lighted, and the slab is viewed by re-flected light at a preferred angle. If the slab be twinned, one portion of theslab will exhibit a bright sheen while the other portion is dull by contrast,see two example
. The Bell System technical journal . s (hours long) again give a simple, strong, andreliable figure. 28 BELL SYSTEM TECHNICAL JOURNAL ample, CT slabs are to be examined the tiltable mounting-table is clampedin the 38° position, and the slab placed crosswise on the table (X-axis normalto line of sight, and beveled edge as shown). Upon moving the viewingscreen to position 1, only lamp 1 is lighted, and the slab is viewed by re-flected light at a preferred angle. If the slab be twinned, one portion of theslab will exhibit a bright sheen while the other portion is dull by contrast,see two examples in Fig. , Test /. The twinning boundary is now pen-ciled in. The viewing screen is then shifted to position 2 which lights onlylamp 2, and the cr\stal moved to right or left so that only one twin is illu-minated. On the screen^^ will be seen an etch-figure similar to one of thefour shown in Fig. , Test 2. If either of the two positive-cut figures areobserved the illuminated portion of the slab is usable, since the CT plate. LAMP HOUSE I/eye chuteV ARMX TRAYOPENING s® ARMt, TRAYOPENING SIDE VIEW. SECTION FRONT VIEW Fig. —The reflection TWINORIASCOPE for detecting twinning (using lamp 1and no viewing screen, position 1) and for determining the orientation or sense-of-cut (usinglamp 2 and the viewing screen in position 2), of AT- BT-, CT-, or DT-cut slabs. Thecut angle is set for a CT slab. miist have a positive 38° orientation. The negative-cut, golf-club,figures are produced by the unusable portion of the plate. The same procedures are followed with the AT, BT and DT plates, ineach case resetting the table to the proper tilt, 35°, 49° and 52°, reflection view of Test 1 is the same for all cuts, and the etch-figures ofTest 2 are nearly the same (being almost identical for the negative-cut por-tions of the slabs). However, in the case of AT and CT slabs the positive-figures represent good portions (since these are positive cuts), and in the c
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
