1891. ] NEW YORK ACADEMY OF SCIENCES. 17 
III. T. 8. Hunt, Feldspar from Chambly, l.c., p. 98. 
Vie a Feldspar from ground-mass of Chambly dike after treatment 
with dilute nitric acid, 1. c., p. 98. 
VY. and VI. H. Forstner, Zeitschr. f. Xtal., viii, 125, 202, 1883 ; Neues Jahrb., 
1884, ii, 171. 
VII. J. H. Sears, On Keratophyre from Marblehead Neck, Bull. Mus. Comp. 
Zo6l., xvi, No. 9, p. 170. 
In the further discussion of the basic dikes it will appear that in 
the close association which they show in the field with bostonite we 
have a mingling of rock types not'unlike that long known at Mon- 
treal,' in many respects similar to that at Marblehead, near Boston,? 
and to the dikes recently brought to notice near Rio Janeiro, 
Brazil.’ In all three localities they are associated with elacolite- 
syenite. This latter rock has not yet been discovered nearer to 
Lake Champlain than Montreal, which is one hundred miles north 
of Burlington. It is not improbable that elaeolite-syenite may yet 
appear in the eastern Adirondacks. 
The Breccia Bostonites. 
On the east side of Shelburne Point, which is just south of Bur- 
lington, and also on the west side, a broad dike (20 feet) outcrops. 
It is undoubtedly continuous between. It is a most remarkable 
rock, and consists of angular pieces of slate and red quartzite ce- 
mented together by an igneous base. The cementing base is not 
very fresh in the attainable specimens, but is clearly of the same 
nature as the ground-mass of the bostonites. The included frag- 
ments are angular and seldom show any absorption into the igneous 
rock. Two explanations may be advanced for this dike. One, that 
it has been intruded ona line of previous faulting and attrition, 
which have broken up the walls and have left loose material to be 
gathered up by the rising magma. This explanation has the greater 
17. S. Hunt, papers cited under analyses I-IV above; also, Geol. of 
Canada, 1863, p. 655. 3B. J. Harrington, idem, 1877-78, p.429. A. Lacroix, 
Sur la Syénite-elaeolithique de Montreal, etc., Comptes Rendus, June 2, 1890, 
p- 1152, and Descriptions des Syénites népéhliniques de Pouzac, Hautes-Pyré- 
nées et de Montréal, etc., Bull. Soc. Geol. France, 3, xiii, 1890, 511-558. 
2 A. Hyatt, Remarks on the Porphyries of Marblehead, Mass., Proc. Boston 
Soc. Nat. Hist., xviii, p. 220, 1876. T. T. Bouvé, The Origin of Porphyry, 
idem, xviii, p. 217. M. E. Wadsworth, The Trachyte of Marblehead Neck, 
idem, xxi, p. 288; Geology of Marblehead, idem, xxi, p. 306; Zircon Syenite 
from Marblehead, idem, xxi, p. 406. W.O. Crosby, Geology of Eastern Massa- 
chusetts. J.S. Diller, The Felsites and their Associated Rocks North of Boston, 
Bull. Mus. Comp. Zool., vii, 165. J. H. Sears, Keratophyr from Marblehead 
Neck, idem, xvi, 167. 
® 0. A. Derby, On Nepheline Rocks in Brazil, ete., Quart. Journ. Geol. Soc., 
London, 1887, p. 457. F. Fr. Graeff, Mineralogisch. Petrograph. Untersuchung 
von Elaeolith-syeniten von der Serra de Tingua, etc., Neues Jahrbuch, 1888, 
li, p. 222. Hunter and Rosenbusch, Ueber Monchiquit ein Camptonitisches 
Ganggestein aus der Gefolgschaft der Elaeolith-Syenit. Tsch., Min. u. Petrog. 
Mitt., xi, 1890, p. 44. 
Vou. XI.—2 
