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STRLE ON MOUNT MONADNOCK. 469 
lines much better preserved than those on less wooded and more 
exposed parts of the mountain. It would be difficult to decide 
what was their prevailing direction. Multitudes ran due east and 
west; some few north and south; some north 10° west; some 
north 10° east; many north 70° and 80° west; many north 70° 
and 80° east. No theory of mountain slides could explain this 
remarkable scratching; the situation seemed to forbid such an 
explanation. These observations were made on many different 
ledges, but all of them within a half mile of each other, and within 
a mile of the north end of the ridge. When a rapid stream with 
a current of three miles an hour passes a rock in its bed, water 
will flow around the rock and meet on its lower side. Do not these 
irregular striæ indicate a changeable and eddying current incon- 
sistent with the motion of a glacier? 
Mt. Monadnock furnishes some suggestions also on the subject 
of erosion. Chemical agency and the action of frost may properly 
enough account for a large amount of rock disintegration. On 
long lines of coast the ceaseless waves of the ocean cause an end- 
less amount of erosion. But the amount of actual planing and 
grinding of the earth’s surface by icebergs or continental glaciers 
Seems somewhat speculative and furnishes small means of meas- 
urement. Whoever has had experience in grinding and polishing 
mineral specimens knows full well that, so long as there are pro- 
tuberances or cavities on the surface he is grinding, he has ac- 
curate means of judging his rate of progress. But when he is 
grinding a flat surface, he has no means of judging from the surface 
itself. So here on a large scale, all along these naked moun- 
tain ridges there are rounded angles and mammillary protuber- 
ances of all dimensions, which are marked with striæ, but have 
never been ground down to a flat surface. They are rounded, 
Scratched and often polished. Is it not possible to reconstruct 
the angles and edges that are worn off and thus have an approxi- 
mate measure of ice erosion? On a hill in Keene there are acres 
of hard quartz rock lying uncovered and much exposed to glacial 
action. The rock is composed of lamine an inch thick, and these 
incline toward the south. When the rock is fractured obliquely, 
the fracture is interrupted by each lamina, so that the edges of the 
laminze project slightly like the serratures of a file. Now all 
Over these sharp serratures there has been much grinding and pol- 
ishing, but the shallow cavities originally between them have rarely 
