470 STRLE ON MOUNT MONADNOCK. 
ly been ground out, and there is no reason for supposing that this 
hard rock has ever been eroded more than half an inch. On Mo- 
nadnock, where the rocks have a regular jointed structure and the 
upper edge alone has been worn off, it is often easy to supply the 
lost angle, by reproducing the contiguous sides. Studied in this 
method an erosion of one or two feet would be as much as is in- 
dicated on all the higher portions of the mountain. On lower 
' ground surfaces are more flat and judgment is at fault. Between 
the northwest and northeast spurs a wide valley opens out toward 
the drift current. This extended valley is filled with mammillated 
rocky protuberances projecting among the spruces which grow 
everywhere between them, from six to ten feet high. This valley 
is in the line of the drift and would be eroded if any place would, 
but the protuberant rocks seem merely to be rounded and the 
roughness of original fracture worn off. 
A few words about the erratic bowlders in this vicinity may not 
be irrelevant. There are bowlders here of a phonolitic character, 
which often contain black porphyritic pebbles fused into their sub- 
stance, making them very easy of identification. These have been 
a subject of special study, and some fifty of them have been found 
in Cheshire county. Prof. Charles H. Hitchcock, who is intimately 
acquainted with New England rocks, says he has never seen such 
rocks, in place, anywhere, except in the vicinity of Ascutney, Vt. 
Ascutney mountain was thrown up in a state of fusion, and its 
heat melted this conglomerate which lay close by it. Ascutney 1$ 
about fifty miles from Monadnock and north 10° west. Two i 
these bowlders lie at the base of- the Monadnock. There is one In 
Keene that must weigh one hundred tons. Many were found near 
together or in the same line; but many more show a great lateral 
divergence. Keene is forty miles from Ascutney, and in that dis- 
tance many bowlders have diverged eight miles, or one mile in five 
from the starting point. These bowlders have been dug out of 
the drift at various depths. While it is difficult to imagine a COP 
tinental glacier making so many and such wide diverging lines, it 
is also difficult to understand how icebergs could have picked up 
these bowlders and polished their hard material on so short a 
journey. 
