780 REGINALD ALDWORTH DALY 
Thus the latter could not in the final stage of consolidation 
cause a serious differential cooling in the marginal part of the 
granitic magma. That there was some influence exerted upon the 
igneous rock is indisputable. Almost universally thin sections of 
the contact-zone exhibit a very marked granophyric intergrowth 
of the quartz and feldspar of the matrix. This micrographic 
development is quite independent of that noted as common about 
the phenocrysts, and is quantitatively much superior in value to 
the latter. The occurrence of the graphic structure in the matrix 
is usually restricted to the contact-zone of not more than a few 
inches or feet in width. It is noteworthy, however, that in parts 
of the Ashuelot area where there are evidences of some crush- 
ing, this structure is found in various parts of the coarse matrix, 
though far from a contact. It doubtless originated as a result 
of rearrangement during the period of stress which the rock has 
here undergone. : 
The origin of the foliation in the porphyritic granite —It is now 
well established that gneisses may belong to three classes which 
in the words of Gregory’ may be named metapyrigen-gneisses, 
clastic-gneisses, and fluxion-gneisses. The first kind is produced 
by the pressure-metamorphism of igneous rocks, the second by 
the complete alteration of sediments. The third division has its 
origin in molten rock-magmas which have undergone ‘fluxional 
movements anterior to complete consolidation in a mass not 
perfectly homogeneous.’? The porphyritic granite of New 
Hampshire owes its foliated structure to the same cause as that 
of fluxion-gneisses. Inshort, this porphyritic gneiss is a porphy- 
ritic granite with a flow-structure. The parallelism among the 
constituents was assumed when the rock was not yet fully 
crystallized out and cannot thus be referred to any metamorphic 
result of mountain-building acting on an already solidified mass. 
It is a primary structure. Since this fact is not as yet demon- 
strated in what has been said, and since we are dealing with a 
™Q. J. Geol. Soc., 1894, p. 266. 
?'T. G. BONNEY, Some Notes on Gneiss, Geol. Mag., 1894, p. 118. Cf. Hitt and 
BONNEY, Q. J. Geol. Soc., 1892, p. 137. 
