SO-CALLED PORPHYRITIC GNEISS OF NEW HAMPSHIRE 695 
face, from the west parish of Concord to the center of Warner, 
where we find the rock itself in place. It is a peculiar rock, 
having large crystals of feldspar uniformly distributed through its 
mass ; they are often glassy, so as to furnish beautiful and striking 
specimens. This bed of granite extends across the state in a gen- 
eral northeast and southwest direction. It is from eight to ten 
miles in width, though often interrupted with veins of granite of 
various texture.”? With the physical difficulties of a rugged, for- 
est-clad country, it was not to be expected that accurate determina- 
tions of boundaries could be made by these geological pioneers. 
To this fact is due the confusion of the ‘‘porphyritic gneiss” and 
associated schists in the published Portsmouth-Claremont sec- 
tion of the Final Report. 
In their section, ‘“‘from Haverhill to the White Mountains,” 
Whitney and Williams again refer to the formation thus: 
“From Meredith to Centre Harbor the rock in place is por- 
phyritic granite, often traversed by beds and veins of fine 
grained, dark colored granite and trap. Some specimens of the 
porphyritic granite, in which the crystals of feldspar are flesh 
colored, are wweny beamtituls o>)... ‘‘From Centre Harbor to 
Plymouth the rock in place is porphyritic granite, traversed by 
occasional beds of mica slate.’’? 
The first distinct mention of the ‘‘porphyritic gneiss” in the 
second (and last) survey of the state, that under the control of 
‘Professor C. H. Hitchcock, occurs in the second annual report, 
1870. The preliminary map issued with that report roughly 
outlines the formation which he calls porphyritic granite. He 
describes it as ‘‘common granite full of large crystals of 
feldspar, generally from one-half of one to two inches long, 
which gives a checked appearance to the ledges. Some portions 
of it have evidently been injected, while the arrangement of the 
feldspathic crystals in parallel lines leads to the suspicion of 
stratification in other cases. When accurately mapped the area 
will resemble the trunk and branches of a decayed tree, the 
‘Final Report on the Geol. of N. H., C. T. JACKSON, 1844, p. 51. 
2Op. cit. pp. 73 and 137. 
