130 The American Geologist. March xs9o. 
and Dr. ITobbs lias gone into considerable detail in his recent- 
ly published paper in the Harvard bulletins on the Great 
Somerville Dike. 
It will be seen from this that there is considerable material 
for petrographical work in this region, and some interesting 
geological phenomena which have, as yet, scarcel}'- been 
touched. In the present contribution it is the writer's pur- 
pose to show by the aid of the accompanying map, how 
abundant the dykes are in one limited area which he has 
worked up, and to give an idea of the detailed geology of a 
region by no means too well known.' 
Kennebunkport is some twenty or twenty-five miles 
beyond the New Hampshire line. The coast is formed 
by bold, rocky headlands and cliffs, between which are found 
long stretches of white sandy beach. At the water's edge 
most excellent exposures are afforded, running sometimes a 
short distance back before the rocks are covered by vegeta- 
tion. They consist of very finely stratified quartzytes, slates 
and jasper}^ la3'ers, with vertical dip and a somewhat 
variable strike, which is indicated on the map. At Kenne- 
bunkport it varies from N. 40 E. to N. 40 W., while fifteen 
miles south on the coast, at Bald Cliff', it is N. 75 to 80 E. 
The strata belong to the Merrimack group of the New Hamp- 
shire survey and are there assigned a position at the close of 
the Archean. These strata are undoubtedly old sedimentary 
beds, whose composition has varied from sandstones to 
shales, as we almost invariably find them in the undisturbed 
sedimentary series, as for instance, the Devonian above 
Ithaca. The sandstone layers are now changed to compact 
quartzytes, while the shales are of pronounced slaty structure. 
Sometimes the slaty cleavage runs obliquely across the bed, 
even when but a few inches thick and between two quartzyte 
layers, showing that the pressure causing it has not been quite 
normal to the bedding planes. 
Very generally above Kennebunkport, great irregular masses 
or bosses of granite are found in these metamorphic rocks. 
They are quite coarsely crystalline, have no regularity of 
form and are often of considerable size. The granite also runs 
off" at times into narrow dikes which extend considerable 
^ The legend of the accompanying map does not allow for the reduc- 
tion of the" original in the engraving. It should read % in.=150 yds. 
