Mineralogy and Geology of the White Mountains. 105 
Arr. IX.— Observations made during an ercursion to the White 
Mountains, in July, 1837; by Oxiver P. Hussarp, M. D., 
Professor of Chemistry, Mineralogy, and Geology, in Dart- 
mouth College. 
; TO PROF. SILLIMAN, 
Dear Sir—In an excursion to the White Mountains, last July, 
I made such observations in Mineralogy and Geology, as my lim- 
ited time and other circumstances permitted ; hoping to add some- 
thing to the little already known of this interesting country, and 
that the facts when known may stimulate others to farther exami- 
nation, they are communicated for the American Journal. The 
details are minute, for I have often experienced the unsatisfactory 
nature of meagre descriptions, and I trust they will not be use- 
less to others who may visit the same points. 
My object is to record facts, and I am happy to say they are 
so numerous, and so decisive that we do not seem to be in the 
region of theory, when we infer at once the nature of those 
causes that have produced the sublime and beautiful scenery that 
adorns the greater part of this state. 
Trap Dikes in Granite, in Dorchester and Canaan. 
In passing from Plymouth, through Dorchester and Canaan, over 
the high ground that separates the branches of the Merrimack and 
Connecticut, boulders of trap were observed one mile east of Dor- 
chester south meeting-house. These are porphyritic, some of a 
light gray, containing a profusion of large crystals of glassy feld- 
spar, with two perfect cleavages—with a few of iron pyrites; oth- 
ers of a much darker ground, with feldspar and black hornblende 
in large and beautiful crystals, and also dark crystallized mica. 
The mica is in smooth nodules, without lustre externally, but pre- 
sents cleavage surfaces of great brilliancy, half an inch in diame- 
ter. It also occurs in crystals penetrating the crystals of feldspar. 
Similar boulders occur in some places in great numbers, on both 
sides of the new road, from Wright’s tavern south nine miles, to 
Daniel Patten’s, in Canaan, near N. E. corner of Hart’s pond. Be- 
tween his house and the guide-board there are several trap dikes 
in granite. No. 1, crosses the road N. by E.—is seven feet wide, 
porphyritic—resembling, in color and crystals, the boulders 
described above ; is uncovered in several places, and its appearance 
Vor. XXXIV.—No. 1. 14 
