72 
NATURE STUDY. 
it from the view of the traveller. Although unknown to the 
geologists ; it was well known to all the earlier settlers and their 
descendants, being frequently mentioned in deeds as fixing cer¬ 
tain boundary lines between adjoining farms. Its shape is 
approximately rectangular, and its longest dimensions are, 
length 38 feet, width 35 feet, height 19 feet. It is difficult, of 
course, to compute its volume, because of its irregularity and 
from lack of definite knowledge as to how far it is buried in the 
swamp muck. It is believed, however, that this cannot be very 
far, as it seems to have been stranded on a pile of boulders of 
lesser size, and in all probability now rests upon them. It 
probably contains between 25,000 and 30,000 cubic feet, corres¬ 
ponding to a weight of 2,000 to 2,500 tons. 
This boulder is composed of the typical New Hampshire 
gneiss, and presents no specially interesting features except its 
size. Of course, such large boulders were not carried very long 
distances, and one naturally looks for the parent ledges within 
comparatively short distances. The nearest exposed ledge to 
this boulder is Rattlesnake Hill, about a mile N. E. by N., and 
if this is about the direction of the glacial movement at this 
locality, Rattlesnake Hill is probably the origin of this boulder. 
In the southern part of the town of Dunbarton, about eight 
miles from Manchester, on the Colby farm, there is another 
massive boulder not mentioned by Hitchcock. This also lies 
in a swamp, and until recently was surrounded by a consider¬ 
able growth of timber. This has just been cut down, however, 
and the boulder now lies quite exposed. This rock is composed 
of porphyritic gneiss, and, so far as could be learned, rests on the 
deposit underlying the sw r amp muck, no other boulders, large or 
small being associated with it. Its longest dimensions are, length 
about 35 feet, width 31 feet, and height 20 feet. Its estimated vol¬ 
ume from these measures and its shape is a little over 20,000 
cubic feet. This corresponds to a weight of about 1800 tons. 
This is probably a fragment of the ledge of porphyritic gneiss that 
extends in a north and south direction through Weare and 
Hopkinton, about S. S. E. A good idea of their magnitude 
