1891. ] NEW YORK ACADEMY OF SCIENCES. 23 
entirely and affords a very beautiful slide. The olivine is seldom 
fresh enough to be certainly identified, but as masses of a green 
alteration product are almost always present its occurrence is proba- 
bly wide-spread. Professor Rosenbusch has, with characteristic 
kindness, looked over some slides of certain of these dikes, and fully 
indorses the determination of them as monchiquite, which had been 
previously made by us. 
The following analyses illustrate the range in composition :— 
No.2: No. 14. No. 21. 
SHGhy eG : : ‘ : 3 - 40.37 45.13 44.30 
Al,Og : / A 5 ; S256 18.06 7.92 
Fe,0, Se oo nee 11.88 25.38 
FeO . 5 : A F : F 0.38 0.32 not det. 
C20" +. Z : 5 , ; ene i fesoyl 10.17 14.67 
MgO . : : : 5 s Ear glee 1.12 1.98 
Re) : E é : : TH OL83 6.06 — 
Na,O . : . : : : ee 129 3.57 — 
Loss . 4 ~ : ; - - 4.47 3.04 4.35 
99.39 99.35 98.60 
No. II also contains P,O,, 0.39. No. 2 and No. 14 were kindly 
analyzed by Mr. W. H. Morrison, graduate student in chemistry 
at Cornell University, and No. 21 by Mr. E. M. Chamot, assistant 
in the same laboratory. The rocks are thus very basic and may, 
as in No. 21, be very low in alkalies. 
The above-mentioned basic dikes and the bostonites are very 
commonly associated with elaeolite-syenite, and we think they 
furnish good reasons for anticipating the discovery of this rock in 
the region of the Adirondacks. The dikes may, however, be an 
extreme southern development of the great eruptive activity near 
Montreal. We think their intrusion accompanied the upheaval of 
the Green Mountains. 
During the field-work of the second summer Mr. A. 8. Eakle, now 
of the geological department of Cornell University, accompanied the 
writers, and acknowledgments are due him for much valuable as- 
sistance. 
Pror. Martin asked the lecturer if the smaller dikes might not 
perhaps be regarded as originating from the larger ones. PRor. 
Kemp replied that they could hardly be so regarded, and added 
that the nearest large masses of eruptive rock were in the vicinity 
of Montreal. 
Meeting adjourned. 
