. Transactions. ck lenses more or less isolated and disconnected; moreover, the pres-sure of the fluid would have to be uniformly maintained until the open-ings were filled, or the walls would collapse. It is obvious that this Op. tit., 309-310. 18 L. C. Graton: Reconnaissance of Some Gold and Tin Deposits of the SouthernAppalachians. U. S. Geological Survey, Bulletin No. 293 (1906) 60. 19 Waldemar Lindgren: The Relation of Ore-deposition to Physical Geology (1907) 2, 107-108. STEPHEN TABER 11 theory is inapplicable to many lenticular veins, such as those of calciteor gypsu
. Transactions. ck lenses more or less isolated and disconnected; moreover, the pres-sure of the fluid would have to be uniformly maintained until the open-ings were filled, or the walls would collapse. It is obvious that this Op. tit., 309-310. 18 L. C. Graton: Reconnaissance of Some Gold and Tin Deposits of the SouthernAppalachians. U. S. Geological Survey, Bulletin No. 293 (1906) 60. 19 Waldemar Lindgren: The Relation of Ore-deposition to Physical Geology (1907) 2, 107-108. STEPHEN TABER 11 theory is inapplicable to many lenticular veins, such as those of calciteor gypsum, formed near the surface in unaltered sedimentary pressure of fluids cannot account for the formation of lenses that aresubdivided by thin partitions of included schist detached from the walls,as illustrated in Fig. 1. In view of all the facts, it must be concluded thatthe typical lenticular veins were not deposited in preexisting peculiar banded structure, sometimes referred to as book. Fig. 1.—Quartz vein in sericite schist near Columbia, S. C. The quartz LENS IS SUBDIVIDED BY THIN PARTITIONS OF SCHIST, AND IN PLACES CONTAINS DE-TACHED INCLUSIONS OF THE WALL ROCK. structure or ribbon-ore, resulting from the alternation of narrowveinlets of ore with parallel sheets of slate or schist, is difficult or im-possible of explanation under any theory of ore deposition in preex-isting openings. Becker and Day20 have called attention to the factthat in some cases it can be shown conclusively that the distribution ofthe slate is not due to faulting. This structure is well developed atmany places along the Mother Lode of California, and also in some of the 20 G. F. Becker and A. L. Day: The Linear Force of Growing Academy of Sciences (1905) 7, 283-284. Proceedings, 12 MECHANICS OF VEIN FORMATION gold and copper veins of the Southern Appalachians. Usually the vein-lets, consisting of quartz or calcite, are lenticular in form, and pinch outto
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