152 W. H. HOBBS REPEATING PATTERNS IN STRUCTURE OF LAND 



Some further districts will be mentioned within which the evidence for 

 a patterned system of fractures is specially clear. A study of the joint 

 system of the Long Lake quadrangle in the Adirondacks of New York 

 State has revealed two rectangular series bisected by a second and similar 

 double series. The one set corresponds to the meridional and trans- 

 meridional directions, the other to directions bisecting the angles of the 

 first. *° From the Elizabethtown quadrangle of this district was taken in 

 1904 the author's type example of checkerboard topography, which showed 

 a rectangular pattern orientated on northwest-southeast and northeast- 

 southwest lineaments.*^ This map is reproduced in plate 9. Kemp 

 and Euedemann, in a very recent paper, say of the drainage of this and 

 neighboring quadrangles :*^ 



"At the headwaters of both the Schroon and the Boquet are some extremely 

 interesting features which also extend into the neighboring quadrangles. The 

 marked northeast and northwest structural lines have caused even the little 

 brooks to follow them. We may start at the source of some little tributary 

 . . . and follow the stream around three sides of a rectangle, each turn 

 being a sharp angular one. 



"The trellised drainage is believed by the writer to be due to a pronounced 

 system of block faulting which has broken up the country into these marked 

 divisions, and which by sheeting the rock along the lines of movement has pro 

 duced the vulnerable portion searched out by the moving water. 



"Besides the northeast and southwest (northwest? W, H. H.) systems of 

 drainage just described there is in this quadrangle and still more in neighbor- 

 ing ones evidence of north and south valleys, and of east and west ones which 

 are older." 



From the vicinity of Cayuga Lake, in western ISTew York, have been 

 taken the remarkably perfect examples of joint systems with rectangular 

 master sets which are now classical, because published in the works of 

 Dana and Hall. Here the two dominating series trend near the meridian 

 and at right angles to it.*^ 



The dominance of three out of the four prevalent fracture directions — 

 northeast-southwest, northwest-southeast, and north-south — as major 

 lineaments for the entire Atlantic border region of the United States was 



*o H. P. Gushing : Geology of Long Lake quadrangle. New York State Museum, Bul- 

 letin 115 (geology 14), 1907, pp. 493-495. 



*i Bulletin of the Geological Society of America, vol. 15, 1905, pi. 4T. 



" J. F. Kemp and R. Ruedemann : Geology of the Elizabethtown and Port Henry quad- 

 rangles. New York State Museum, Bulletin 138, 1910, pp. 16-17. 



<3 H. S. Williams, R. S. Tarr, and E. M. Kindle : Geologic atlas of the United States, 

 Watkins Glen-Catatonk folio (field edition). Washington, 1909, p. 109. 



