Petrography of Mount Orford. — Dresser. 15 
a third forms the Hue of hills along the international boundary 
line between the states of New Hampshire and Maine on the 
one hand and the "eastern townships" of the province of 
Quebec on the other.* 
A little to the east of the Sutton ridge and parallel to it 
there is for some distance north of the Vermont boundary 
line a series of irregular hills, which have a quite different 
origin from the ranges on either side of them. While the lat- 
ter have been produced chiefly by the crumpling and folding 
of sedimentary strata the former are of volcanic origin, being 
the remains of immense outputs of lava, now greatly altered 
in character and reduced in amount, which were ejected from 
a series of volcanoes or fissure eruptions, probably caused by 
the weakening of the sedimentary strata in the process of the 
folding which produced the Sutton mountains. 
The largest of these ignccjus masses is that which com- 
prises mount Oxford, the area of which is not less than 
twenty square miles. If its average hight above the surround- 
ing country be estimated at 1,000 feet,'? the mountain at pres- 
ent represents four cubic miles of lava which have been ex- 
truded in this one mass, and it must also be remembered that a 
considerable portion of the mountain has doubtless been re- 
moved by denudation, for besides the action of subaerial agen- 
cies, it has also suffered from glaciation, even upon the sum- 
mit.f 
The densel}' wooded nature of the mountain as v/ell as 
its precipitous sides in the only practicable direction of ap- 
proach make the mountain difficult of access and render a de- 
tailed field examination at present impossible. Yet well known 
paths of ascent on the southern side give almost continuous 
exposures from the Canadian Pacific railway at the base to the 
summit, while, as has been pointed out by Dr. Ells.lj: a unique 
*Dr. K. W. Ells. Rep. Geological Survey of Cauuda, Vol. II, 1886, Part J. 
and map, and Vol. VII, 1894, Part J. and map. 
§The Canadian Pacific Railway at Miletta Station is 905 leet above mean 
sea level. P. Alex. Peterson, Chief Engineer, C. P. Ry. 
Dr. Ells (op. cit.) found the height of the summit to be 2800 feet above 
sea level by aneroid measurements which were subsequently corroborated by 
Mr. Chalmers. (An. Rep. Geol. Surrey of Canada, Vol. X, Part J. 
Messrs. Evans and Lerov {Can. Rec. Sci. pp. 225-7, July 1900) find the 
total elevation somewhat less, viz : 2650 feet. 
^Can. Rec. Sci., July 1900, pp. 223-5. 
t.im. Rep. Geol. Survey of Canada, 1894-, Part J., pp. 59-62. 
