THE ORIGIN OF FOLIATED CRYSTALLINE ROCKS 243 
the crystallization of primary gneisses so as to cause the develop- 
ment of elongated forms in the minerals must also expect to find in 
the texture of these rocks many other features common to the 
metamorphic type. It must be supposed, for example, that along 
with marked development of cleavage faces would be a general 
tendency toward the series of form development characteristic 
of “crystalline schists’? as outlined by Grubenmann. ‘The writer’s 
observations seem to corroborate this. In short, the texture of 
primary gneisses appears to be intermediate between the igneous 
and the metamorphic types, being more like the latter according 
as the movements producing the banding continued late in the 
period of consolidation. 
CONCLUSIONS REGARDING THE TEXTURE OF PRIMARY GNEISSES 
FROM THE MODE OF THEIR INTRUSION 
Various types of rock bodies have been described as possessing 
an original banding and it is natural to suppose that the methods 
of their intrusion must differ considerably. The size of the bodies 
varies from dikes, such as are characterized by parallel feldspar 
phenocrysts, to masses of batholithic proportions. In the case 
of many of such dikes it can hardly be doubted that the foliation 
was produced by movements in the magma since the rocks cut by 
the dikes sometimes show no evidence of rock flowage. The origin 
of the banding of the gneiss in certain batholiths, attributed by 
Lawson and others to movements prior to the complete solidifica- 
tion of the rock seems, however, to be considered more uncertain 
by many geologists. The identification of this type is, however, 
more important than that of the smaller bodies and its origin will 
be considered more fully. 
The association of igneous activity and batholithic intrusion 
with periods of mountain building" is well recognized. Those who 
have described batholithic masses as possessing a primary banding 
are in general agreement that at the time of the intrusion crustal 
deformations were active and continued so during the solidification 
of the igneous mass. The intruded rocks have generally been 
considered to have undergone rock flowage, and, accordingly, no 
tR. A. Daly, Am. Jour. Sci., 4th Ser., XXII (1906), 195-216. 
