Notes oil Monhegan Island. — Lord. 331 
essentially denuded the islands of all transported material, ex- 
cepting the larger bowlders and small areas (left open on the 
map) of re-assorted drift at the head of sheltered inlets. 
Apart from the secular movements already noted the re- 
gion ha? undergone excessive orographic disturbances, result- 
ing in longitudinal and transverse faulting, as well as in a com- 
plex system of both vertical and horizontal jointing. The 
effect of crushing is also plainly seen in the minute fractures 
and rifts common in almost every hand specimen. 
All important fracture extending through the northern 
end of Manana island in a N. 55° E direction across J\Ionhe- 
gan forms a marked topographical feature of both islands. 
Excessive shearing in this direction has rendered the rock 
in the vicinity of Manana harbor semi-schistose, or produced 
a highly brecciated structure (western slopes of Light House 
hill). 
The E-W faulting is not so extensive as the longitudinal, 
and plainly noticeable only in the neighborhood of the trans- 
verse depressions mentioned above. 
One other important line of movement, possibly of more 
recent date than those already mentioned, extends in a N 55°- 
60° W. direction, corresponding exactly with the strike of a 
series of granitic dikes to be discussed later. 
Although varying considerably in mineral composition the 
Monhegan mass, as a whole, consists of a coarse grained oli- 
vine-noryte, very rich in feldspar, and resembling, in part, at 
least, the olivine bearing anorthosyte of the Saguenay District, 
Canada.* 
While this rock is (juite common in New Hampshire, and 
eastern New York.t its exact equivalent has not hitherto been 
found in Maine, although the gabbroitic-diabase (black gran- 
ite) occurring on St. George peninsula, Addison Point and 
*See F. D. Adams; Amer. Jour. Sci., Vol. 50, 1895, p. 58; and Ann. 
Rep't. Geol. Sur. Canada, Vol. VIII, (J) 1895, p. 91. 
tSee G. W. Hawes; Geology of New Hampshire. Vol. Ill ( Lith- 
ology) p. 168-169; G. H. Williams: The Gabbros and Diorites of the 
"Cortlandt Series," on the Hudson River near Peckskill, N. Y.. Amer. 
Jour. Sci., Vol. XXXV, Feb. 1888, p. 438; ibid. Vol. XXXII. 1886, 
pp. 26-41; C. H. Symth, Jr.: On Gabbros in the South Western Ad- 
irondack Region. Amer. Jour. Sci., III. Vol. 40. 1894, p. 55, and 
Bull. Geol. Soc. America, No. 6, 1894-5, P- 261; J. F. Kemp: Gabbros 
on the Western shore of Lake Champlain, N. Y. Geol. Soc. .Amer., 
Bull., Vol. 5, p. 213. 
