696 NSH CSONEULIO! AIO VM OVR AIS. JOVAIL NZ 
branches corresponding to the veins which have been injected 
from the original mass." 
In the yreporte fornvthe mext year) kirofessonmaitehcoes 
adopted the view which was held throughout the later publica- 
tions of the survey. On the map, of a scale of five miles to one 
inch, he differentiates the Lake Winnipiseogee and White Moun- 
tain areas, and gives a brief description of the rock, to which 
INS VENIDXES WS MENS “lxorplyiatine emesis, Isle Sayse Wins 
is an ordinary gneiss, carrying numerous crystals of orthoclase 
or potash-feldspar, from a quarter of one to two inches long. 
The longer axes may be parallel to the strike or arranged 
helter-skelter. It passes into granite with the same porphyritic 
peculiarity of structure. . . . . We suppose this to be the oldest 
formation among the mountains. Geologists speak of a rock of 
this character as common in the Laurentian in various parts of 
North America and Europe.’’? 
At the twenty-first meeting of the American Association for 
the Advancement of Science, held in 1872, Professor Hitchcock 
expressly referred the ‘“‘prophyritic gneiss” to the Laurentian$ 
and noted the common parallel structure of the rock which he 
concluded to be the trace of an almost obliterated stratifi- 
cation. 
An indication of doubt as to an exact correlation appears in 
Professor Hitchcock’s ‘Classification of the Rocks of New 
Hampshire,” published in 1873.5 He divides the various forma- 
Second Ann. Rep. upon the Geol. and Mineralogy of N. H., 1870, p. 33. 
2 Geology of New Hampshire, 1874, Vol. I, p. 33. 
3Explanation of a New Geological Map of New Hampshire. Proc. A. A. A.S., 
1872, p. 134. 
4Recent Geological Discoveries among the White Mountains, N. H. Proc. A. 
A. A.S., 1872, p. 135. In this paper the author states his grounds for the correla- 
tion, viz., that of lithological similarity between the porphyritic gneiss and the Lau- 
rentian of Canada and Europe. At each of the next two meetings of the Association, 
he reaffirmed his position that there is nothing older in the state than the porphyritic 
gneiss which was held to be Archean in age. See Geological History of Lake Winni- 
piseogee. Proc. A. A. A. S., 1873, B. p. 122, and the Physical History of New 
Hampshire, zézd., 1874, B. p. 76. 
5 Proc. Bos. Soc. Nat. Hist., Vol. XV., p. 304. 
