. The Quarterly journal of the Geological Society of London. Figs. 11 & 12.—11. Veins seen 200 yards above the boathouse. 12. part 3] THE PSEUDOTACHTLTTE OF PARIJS. 205 Fig. 13.—PseudotachyJyte 200 yards above the courses (text-figures 2, 3, 9-13) and their direction is entirely independentof the foliation of the granite (text-figures 3, 5, 6, 8, 10). They thicken and thin repeatedly and rapidly (text-figures 6, 7, 9, 10-12),give off branches at high and low angles (text-figures 2-4, 7, 8, 10-12), andoften anastomose in the most complicated way (text-figures 10-12). In innumerable
. The Quarterly journal of the Geological Society of London. Figs. 11 & 12.—11. Veins seen 200 yards above the boathouse. 12. part 3] THE PSEUDOTACHTLTTE OF PARIJS. 205 Fig. 13.—PseudotachyJyte 200 yards above the courses (text-figures 2, 3, 9-13) and their direction is entirely independentof the foliation of the granite (text-figures 3, 5, 6, 8, 10). They thicken and thin repeatedly and rapidly (text-figures 6, 7, 9, 10-12),give off branches at high and low angles (text-figures 2-4, 7, 8, 10-12), andoften anastomose in the most complicated way (text-figures 10-12). In innumerable cases they thin out and terminate blindly (text-figures 1-3,7, 8, & PI. XVII, fig. 1). The contact with the surrounding granite, as seen with the naked eye, isperfectly abrupt. The granite is never sheared parallel to the course of theveins, its texture remains unchanged, and the felspars continue to showlarge bright cleavage-faces and straight twinning lamellae, right up to thesurface of contact (PI. XIX. fig. 1). The junction-line is often nearly straight for distances of many feet,especially in the case of those veins which are not more than a few inchesthick (text-figures 1, 2, 4, 5, & PI. XVII, fig. 1) ;
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Keywords: ., bookcentury1800, bookdecade1840, bookidquarte, booksubjectgeology
