. Bulletin of the Geological Society of America. Geology. CONTROLLED FRACTURE FIELDS OF NORTH AMERICA 149 have been found to run parallel to the northeast-southwest lines of the drainage network^ and by utilizing the information derived from this source concerning spacing, Doctor Miller has been able successfully to^ follow out the continuations of interrupted ore bodies. In both these ex- amples it should be noted not only that the drainage net- work betrays a definite ori- entation of waterways along either the cardinal or their bisecting directions, but that there is a subequal spacing of t
. Bulletin of the Geological Society of America. Geology. CONTROLLED FRACTURE FIELDS OF NORTH AMERICA 149 have been found to run parallel to the northeast-southwest lines of the drainage network^ and by utilizing the information derived from this source concerning spacing, Doctor Miller has been able successfully to^ follow out the continuations of interrupted ore bodies. In both these ex- amples it should be noted not only that the drainage net- work betrays a definite ori- entation of waterways along either the cardinal or their bisecting directions, but that there is a subequal spacing of the streams in units of different orders. Essentially the same orientation and spacing is betrayed by one of Harder's published maps from southwestern Wiscon- sin.^^ Buckley has shown that the prevailing joints in practically all quarries of Wisconsin indicate a domi- nance of the four directions toward the cardinal points and along their lines. He says:^^. Figure 24. — Drainage Map of the Area about Rockland^ in northern Michigan Showing an arrangement of streams on north- south, east-west, and northwest-southeast lines, bisecting '^^^ divisions in the margin represent miles. (Nel- " list's map) "As will be seen by the accompanying map, the joints of the sedimentary rocks strike in four main directions. The prevailing general direction of the joints is northeast and southwest. The other directions are northwest and southeast, east and west, and north and ; On the north shore of Lake Superior the vertical dikes of Keweenawan rock are in two series, one of wide dikes trending northeast to southwest, the other of narrow dikes about northwest to southeast.^^ Like directions M Harder : The Richland Center District. Loc. cit, pi. 3. '3 E. R. Buckley : On the building and ornamental stones of Wisconsin. Bulletin of the Wisconsin Geological and Natural History Survey, No. 4, 1898, p. 459, pi. 49. 8< A. C. Lawson : Twentieth Annual Report of the Geological and
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