314 Rogers's Account of two Remarkable 
less easily destructible, which occur for many miles north-west 
of it, smoothed and rounded by their mutual attrition, and 
mingled in the most heterogeneous manner, these trains con- 
sist of one special kind of rock, readily distinguishable from 
every other in the region both by its composition and external 
aspect. It has a distinct greenish color, is excessively tough, 
and is partially, and in some masses almost entirely, crystal- 
line. The fracture and composition plainly show it to be a 
rock altered by igneous action, and in that intermediate state 
towards full crystalline development, in which a determination 
of its component minerals is attended with some uncertainty. 
It contains much glassy felspar in apparently incipient for- 
mation, a green mineral like Nephrite, and perhaps. Picros- 
mene. So well marked are all its external features, that the 
observer finds no difficulty in recognizing any isolated frag- 
ment of it; he perceives, at a glance, that the blocks do not 
belong to any of the zones of argillaceous or talco-argillaceous 
slates, vitreous sandstones, and semi-crystalline limestones, 
which the trains cross, but he identifies them at once with a 
particular hard and massive stratum found nowhere but in the 
very summit of the high ridge in Canaan, where it projects, 45 
a narrow rib, along the sharp and somewhat broken crest. 
After tracing either of the two long and narrow belts of angu- 
lar stones, north-westward, for many miles, across successive 
valleys and their intervening ranges of hills, and finding, as 1t 
were, no parentage in any of the strata beneath for these far- 
strewn surface blocks, the geological traveller feels extreme 
amazement when, upon clambering to the torn and narrow 
crest of the Canaan ridge, he sees at last the separate source 
of each of these immense streams of stones. There each train 
suddenly terminates, and there, in the very crest of the 
mountain, is the material from which the whole collection of 
fragments must have been derived. As observed by Dr. 
Hitchcock, the very places whence the fragments were "ne 
tured, are still visible. The observer is surprised to notice 
that each train originates in a distinct depression in the crest 
