THE 
AMERICAN GEOLOGIST 
Vol. XXIII. MAY, 1899. No. 5 
ON SOME DIKES IN THE VICINITY OF 
JOHNS BAY, MAINE. 
By F. Bascom, Brju Mawr, Th. 
(Plates VIII, IX, X and XI.) 
Introduction. — The repeated occurrence of trap dikes along 
the coast of Maine has already been noted and their char- 
acters at several localities have received detailed descriptions. 
The literature of the subject is given in a recent article in this 
magazine.* 
To the localities listed by Mr. Lord may be added Ruther- 
ford's island and Thrumbcap island. These islands, lying be- 
tween Johns bay and the mouth of the Damariscotta river, are 
about five miles east of Boothbay and forty miles northeast of 
Portland. Rutherford's island is separated from the mainland 
by a narrow channel spanned by a bridge. Thrumbcap island, 
three-fourths of a mile south of the southern extremity of 
Rutherford's island, forms with that island the continuation of 
the narrow foreland lying between the Damariscotta river and 
Johns bay. 
The fiord-like character of the seaboard is impressive in 
this region as elsewhere on the coast of Maine and the mani- 
fold and varied indentations of the shore-line furnish scenery 
unsurpassed in picturesque quality. While the coast is rugged 
the relief of the land is not great. The highest point on 
Rutherford's island is one hundred and fifty feet above 
sea-level while the adjacent mainland reaches the hight of 210 
*E. C. E. Lord: On the Dikes in the vicinity of Portland, Maine. 
The American Geologist, vol. XXII, No. 6, Dec, 1898, p. 335. 
