Proceedings of the United States National Museum . example illustrated in figure 14 is thesame case except in theshape of the hour-glasspattern. In the case of these crystals, which are thesimplest examined, the anomalous optical be-havior can most easily and satisfactorily be ex-plained by assuming an underlying normal preh-nite crystal, of uniform thickness and normaloptical properties, overlain by a scale havingthe outline of the hourglass and made up oftwo crystal individuals oriented at right an-gles to each other and at 45° to the underlyingcrystal. All of the anomalous birefringence,dis
Proceedings of the United States National Museum . example illustrated in figure 14 is thesame case except in theshape of the hour-glasspattern. In the case of these crystals, which are thesimplest examined, the anomalous optical be-havior can most easily and satisfactorily be ex-plained by assuming an underlying normal preh-nite crystal, of uniform thickness and normaloptical properties, overlain by a scale havingthe outline of the hourglass and made up oftwo crystal individuals oriented at right an-gles to each other and at 45° to the underlyingcrystal. All of the anomalous birefringence,dispersion, and confused optical figures can besimply accounted for by this interpretation. The crystal illustrated in figure 15 is the plate is rectangular and is boundedonly by the pinacoids a (100) and h (010). When the main crystalc — c is at the position of extinction, which is parallel to its edges,the hour-glass portions show only a very faint luminosity, whichgives the same effect as the preceding with the sensitive tint, but.
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Keywords: ., bookauthorun, bookcentury1800, bookdecade1870, booksubjectscience
