64 Col. McMahon—Granite of the Himalayas. 
Whether he holds that the granite was injected in a fluid, or in a 
partially consolidated condition, is not so clear to me. Possibly if 
there is any apparent divergence in our views, it may be owing to 
my not having expressed mine in sufficient detail. 
Mr. Oldham, in the extract I have quoted, speaks of the condition 
of the granite when foliation was produced as “ solid but still heated.” 
(The italics are mine.) In my papers I have avoided the use of the 
word solid, and preferred to speak of the granite as being in “a 
partially cooled and imperfectly viscid’ condition, or as an “im- 
perfectly consolidated”? mass; but by the use of these expressions 
I contemplated a considerable advance towards solidity. In my 
article in the May, 1887, number of this Macaztnz, I stated that 
the ‘semi-plastic mass was subjected to enormous pressure; the 
mica was crumpled, and the crystals of felspar were cracked and 
ruptured.” These results, ] need hardly say, could not have been 
produced unless the solidification of those portions of the rock in 
which they are to be observed was in a somewhat advanced stage. 
But, on the other hand, I do not think it necessary to hold that the 
granite at the moment of intrusion was everywhere in a state 
of maximum viscidity. Its condition, I apprehend, varied from 
point to point; being in some places in the normal condition of a 
liquefied granite, whilst at others it was almost completely made up 
of minerals that had already crystallized out of the magma. There 
were also, we may suppose, numerous gradations between these two 
conditions. ‘That this was actually the state of the granite I infer 
from the examination of thin slices under the microscope, and from 
the appearance of the rock in the field. In some places it is a 
perfect granite—in others it is a perfect schist. In specimens from 
some spots the microscope reveals the marks of crushing; in those 
from other localities these marks are absent. 
At pages 76-77 of the February, 1587, number of this Macazinr, 
I have suggested a few reasons to account for a similar state of 
things in the Lizard gabbro. The rapid, and often apparently 
capricious, passage of rocks of this class from a granitic to a foliated 
condition, suggests very complex questions which cannot be dis- 
cussed in detail on the present occasion; but though I shall not 
now attempt to explain at length why traction, shear, and pressure, 
operating on an imperfectly consolidated eruptive rock, fail to 
produce perfectly uniform results in every portion of the erupted 
mass, still, it may be as well to briefly allude to some of the causes 
which, in my opinion, may have produced these results in the 
Dalbousie granite. One reason has already been alluded to, namely, 
the want of uniformity in the consistency of all portions of the 
erupted mass at the moment of eruption. Micro-petrologists are 
already familiar with the idea that a more or less complete lique- 
faction of deep-seated igneous rocks takes place when the pressure 
under which they have been held is relaxed by portions of these 
rocks finding a vent at the surface ;—instance the partial refusion of 
the porphyritic quartz crystals in quartz porphyries. The order in 
which minerals fuse, or crystallize, depends, to mention one factor 
