. Annual report. New York State Museum; Science; Science. [62 NEW YORK STATE MUSEUM amples of the effect of the dragging pressure and the percussive force of the boulder-shod ice. The rock is too hard to accept much furrowing or mass removal on the flat surfaces, but its brittleness favors the production of fractures due to compression and to strik- ing force. Of these features two classes will be briefly described. The hard boulders held as planes and hammers in the bottom ice have produced two kinds of curving fractures, one class convex up- stream or toward the boulder, the other convex dow
. Annual report. New York State Museum; Science; Science. [62 NEW YORK STATE MUSEUM amples of the effect of the dragging pressure and the percussive force of the boulder-shod ice. The rock is too hard to accept much furrowing or mass removal on the flat surfaces, but its brittleness favors the production of fractures due to compression and to strik- ing force. Of these features two classes will be briefly described. The hard boulders held as planes and hammers in the bottom ice have produced two kinds of curving fractures, one class convex up- stream or toward the boulder, the other convex downstream or con- cave toward the boulder. Those with the concavity facing down- stream, that is to say, with the convexity toward the producing tool, fall under the category of " cones of percussion" or " chatter ; Many excellent examples of these concentric fractures are seen, some of large size or up to 10 inches of arc and forming from one quarter to one third of the circle. Sometimes the parallel con- centric fractures are closely crowded, several within an inch, but are usually somewhat more open, three or four or less to the inch. Figure 13 is traced from a " rub " taken by the road near the house. Six Inches Fig. 13 Chatter fractuies of William Northrup, 3 miles northwest of Redwood and 3 miles east of Alexandria Bay, and about Y\ of a mile northeast of the curved scorings described above. In this case 11 fracture lines lie within 4 inches along the axis of the curvature, most of them being. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original New York State Museum. Albany : University of the State of New York
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectscience, bookyear1902
