GREGORY.] 
TRACHYTES. 
109 
buried and only recently brought to light by denudation. This ques- 
tion will be discussed in connection with the geologic history of the 
region. 
RHYOLITES OF THE HILLS ADJOINING HAYOTACK. 
The rock forming the hills immediately north of Haystack is in 
general closely similar both in general aspect and in microscopic struc- 
ture to that forming the main mass. The hill on lot 115 is composed 
of rock almost identical with Haystack in structure, but appears to 
have suffered some brecciation and occasionally contains fragments of 
foreign material. The rock forming Pyles Hill conforms well with 
the typical rhyolites, and, because of the amount contained in the hill 
and the unaltered condition, might well have been described as the 
type, with Haystack proper as an additional occurrence. About the 
center of the west line of lot 115 the rhyolite exposed is of a white or 
Rhyolite. Slates. 
Fig. 3.— Diagram of Haystack Mountain. 
flesh color, and a microscopic examination shows it to be a sort of 
transition form between the true rhyolites and the quartz-trachyte of 
Quoggy Joe Mountain. To the west of Haystack, along the branches 
of Welts Brook, the rhyolite rocks have been cleaved and broken and 
afterwards recemented, so as to present the appearance of a coarse 
breccia. In one place along the south line of lot 100 an extensive 
exposure of coarse volcanic ash was discovered, which will be described 
on page 127. A careful determination of the details of the rock for- 
mation about Haystack is impossible until land is cleared and the 
swamps are drained. 
TRACHYTES. 
Trachytes were found in three different localities in Aroostook 
County. One mass constitutes Hedgehog Mountain, another is found 
in Chapman Township, and a third area of doubtful trachytes forms 
low hills along a branch of the Caribou Stream in Woodland Township. 
