110 CONTRIBUTIONS TO THE GEOLOGY OF MAINE. [bull. 165. 
HEDGEHOG TRACHYTE. 
Hedgehog Mountain is probably the largest single mountain mass in 
eastern Aroostook County. It is a ridge extending some 4 to 5 miles 
in a northeast-southwest direction and rising about 1,000 feet above 
the stream beds at its base. It is surrounded by lakes and swamps, 
except on the northeast, in which direction it extends for a mile or 
two as a flat-topped hill. The mountain is thickly overgrown with 
trees and brush, and this, together with the great depth of the talus, 
makes an examination of the structure and rock formation impossible 
except at the very highest points, where the cliffs are exposed, and the 
continual splitting off of the blocks on the east and west sides of the 
mountain has left a bare, jagged ridge, in places scarcely 100 feet wide. 
The whole mass is separated into great blocks by two prominent 
cleavage planes, one of which strikes N. 80° W., the other N. 20° E. 
The blocks themselves in the ledge and on the talus slope suggest an 
indurated f eldspathic lava. When the region about this mountain can be 
more fully explored interesting relationships will doubtless be brought 
out, but at present it is advisable to limit the discussion to a descrip- 
tion of the occurrence and character of the rock composing the mass. 
CHAPMAN TRACHYTE. 
The Chapman trachyte occurs in the northwest corner of the town- 
ship, on the north-south road near the west township line, where out- 
crops were seen on a hill about 1 mile south of the Presque Isle River. 
All the region south, east, and west of the river is forest and swamp 
land, with the exception of a few cleared farms along the road. It is 
on one of these farms that the trachyte occurs, close by the house and 
in the adjoining field. The outcrop occurs as rough ledges and jointed 
tabular rocks, rising but a few feet above the general level of the field, 
and in all cases is quite limited in extent. The several exposures seen 
indicate an area of about 5 acres, but it is likely that further exam- 
ination, especially after the land is cleared, will show that the mass 
covers several square miles and may be connected with the little-known 
Hedgehog Mountain to the west. At present, however, the swamps 
and products of forest decay effectually conceal the rocks, and nothing 
more definite can be said as to its relations to the other formations of 
the region. ' 
WOODLAND TRACHYTE. 
The outcrops of trachyte at this locality have been too little studied 
to warrant an extended description. 
QUARTZ-TRACHYTES, 
Quartz-trachyte will be described from two localities in the region 
included in this report. It forms the group of hills west of Fort Fair- 
