INTRODUCTION. 11 
All of the granites of Maine are believed to belong to the same 
great period of igneous activity. This conclusion is based on (1) 
their general lithologic similarity, the differences between granites 
of different areas being no greater than those observed between dif- 
ferent parts of a single area; (2) the nearly continuous extension of 
certain granite belts for long distances, notably the belt which ex- 
tends with slight interruptions from New Brunswick to Jonesport 
and thence to Mount Desert, Deer Isle, Vinalhaven, and Tenants 
Harbor; (3) the fact that certain areas of granite are connected by 
belts that are intensely intruded with granitic rocks, thus suggest- 
ing that the granite areas may be continuous beneath the present 
surface; (4) the fact that most of the granites of the other New 
England States appear to be of about the same age as those of Maine, 
thus suggesting a single period of great igneous intrusion throughout 
the whole New England province. 
There can be little doubt at least of the contemporaneity of the 
granite of the Perry basin, on the eastern border of Maine, with 
that of Vinalhaven, since the granite forms a i:>ractically continuous 
belt between these two localities, and relations are shown in these 
two regions which approximately fix the age of the granite. In the 
Silurian rocks of the Perry region no granite pebbles are found, but 
such pebbles, plainly derived from the main granite masses of this 
region, occur abundantly in the conglomerate at the base of the 
Perry formation, which is of late Devonian age. The granite of the 
Perry region is therefore late Silurian or Devonian in age. Evidence 
confirmatory, but less complete, is found in the Vinalhaven region, 
where the granites intrude surface volcanics of Niagaran age. 
SCOPE OF THIS REPORT. 
This investigation was undertaken at the request of the Maine State 
Survey Commission, which cooperated with the United States Geo- 
logical Survey in meeting the expenses of the field work. The plan 
of this study of the Maine granites provided for both the scientific 
and the economic phases of the subject, and it is believed that the 
author has succeeded in making this report an important contribution 
along both these lines. 
Discussion of the granites and associated rocks from a purely petro- 
logic standpoint has been omitted, and no chemical tests have been 
made except as the chemical composition is believed to affect the dura- 
bility of the stone. The observations on the relation of the bands of 
knots to flow structure in the granite, on the parallelism of banding 
with sheeting and rift, on the relation of sheeting to the surface of 
the rock, on the cause of the sheeting, and on the spacing and distri- 
bution of joints furnish data of high scientific value, which can be 
used by the geologist interested in the physics of intrusion. Several 
