780 REGINALD ALDWORTH DALY 
of the nature of a foreign body embedded in the matrix. Thus, 
it would behave in the same manner as the truly exotic inclusion 
and a conspicuous alignment would result. It was observed in 
the field that, as arule, the greater the dimensions of the pheno- 
crysts, the more clearly was the structure displayed. 
It is clear that the porphyritic granite with its elongate 
feldspar phenocrysts abundantly fulfills this criterion. In fact, 
the study of it suggests that plutonic rocks would more generally 
show a flow-structure were their constituents more varied in 
shape and relative size from the usual forms. 
Quite rarely a broad banding is observable which is the result 
of the juxtaposition of layers containing different proportions 
of the phenocrysts." 
6. The negative criterion is valuable and in this New Hamp- 
shire case is most conclusive. If it canbe shown that mountain- 
building could not induce the parallel structure in any secondary 
fashion, z. ¢., by the pressure-metamorphism of consolidated, 
igneous or sedimentary rocks, we can fairly assume that the only 
other recognized cause has been operative. The evidence 
necessary therefore is threefold. 
First, it may be derived from the study of foreign inclusions. 
The schistosity of the horses in all the observed localities where 
they occur within the porphyritic granite was evidently produced 
before the existence of that rock in its present state of crystalliza- 
tion. In practically all cases where comparison was possible, 
the excellence of this structure in any one inclusion was reflected 
in its parent-terrane. As the one varied from massive to 
schistose with a high degree of fissility, so did the other. Now 
the perfection of the schistosity was found to be irrespective of 
the attitude of the horses, z. e., whether they were in parallel 
arrangement or not. Callaway used the correlative of this 
principle as an aid in determining the nature of the foliated 
granites of Northern Donegal.*? He finds in them inclusions of 
massive diorites. His conclusion is, that on any theory of a 
*Cf. G. H. WILuiAMs, Bull. U. S. Geol. Surv., No. 28, p. 26. 
? READE, Origin of Mountain Ranges, p. 139. 
