. The Bell System technical journal . ss and the electrical senseof the illuminated portion of the slab. The handedness is as indicated by Land R in each etch-figure of Fig. , and the electric axis is ± to the rightor left as indicated by the -|- and — signs. Best etch-figures are obtained m the twinoriascope with fine ground (400carborundun) slabs which have been given a strong etch (40 minutes in 50% 30 BELL SYSTEM TECHXICAL JOURNAL HF). Stronger etching is not deleterious. Very strong etching gives mod-erately good ligures with sawn or coarse ground slabs. For Test 1, alone,weaker etche
. The Bell System technical journal . ss and the electrical senseof the illuminated portion of the slab. The handedness is as indicated by Land R in each etch-figure of Fig. , and the electric axis is ± to the rightor left as indicated by the -|- and — signs. Best etch-figures are obtained m the twinoriascope with fine ground (400carborundun) slabs which have been given a strong etch (40 minutes in 50% 30 BELL SYSTEM TECHXICAL JOURNAL HF). Stronger etching is not deleterious. Very strong etching gives mod-erately good ligures with sawn or coarse ground slabs. For Test 1, alone,weaker etches would suffice. Under properly controlled conditions of slabpreparation and instrument operation Test 2 might be eliminated, forunder such conditions the negative-cut portion of the slab is bright, thepositive-cut portion is dark. Under shop conditions this means of detectingsense of cut appears to be not reliable, especially with untwinned slabs (whichare either all bright or all dark). The addition of Test 2, however, gives EYE. Z - AXIS f TURN LJ TABLE Fig. —The direction and sense of the electric axes of a sand-blasted and etched rawquartz stone may be determined by reflection of light from the facets. These samefacets are utilized in Test / of the twinoriascope, Figs. , complete reliability, for if etch-figures are obtained the sense of cut is ob-vious, if no figures are obtained the slab can be returned for further principle of Test 7, above, has been applied by W. L. Bond to a lab-oratory instrument for determining the direction and sense of the X-axes inraw quartz stones prepared with a sand-blasted and etched surface. Withthe stone mounted rotateably about its Z-axis (previously determined byconoscope or inspectoscope), and a light beam properly projected onto thestone, reflection of the light beam to an eye piece or viewing screen will occurwhenever the facets come into proper angular position, see Fig. approximate di
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
