THE QUIZZYHOTA LACCOLITE 85 
The arguments employed here rely on the theory that igneous 
magmas are solutions not necessarily at very high temperatures. 
I shall endeavor to establish the fact that such magmas—which 
in their injection state may be entirely fluid or may consist more 
or less of crystals already formed, but yet, as a whole, plastic under 
pressure with the help of solvent water—have certain properties 
which cause them to crystallize in one standard type with structure 
and composition constant, no matter what amount of extraneous 
rock they may have absorbed. I shall apply to a rock magma 
and the resulting igneous rock the laws which govern the develop- 
ment of single crystals, such as andalusite, in among rocks of totally 
different composition, assuming that what holds good for individual 
crystals, also applies to collections of crystals such as igneous rocks 
are. 
The argument will be, in short, that the original molten or fluid 
magma works its way up into the rocks near the surface of the 
earth; the release of pressure sets free a certain equivalent of heat, 
or more probably chemical activity, which is employed in absorbing 
the rocks encountered. As portions of the country rock become 
digested, the bulk of the igneous rock at any one time preponderates 
over the including fragments, and the mineral composition of the 
magma asserts itself in that it takes from the fragments it is 
absorbing such substances as are suitable to the formation of the 
rock of the type represented by the magma, and unsuitable material 
is passed downward along the supply dykes. Dykes consolidated 
before the waste material has been removed are represented in the 
dolerite dykes of the Rainy Lake région in Canada; for instance, 
the White-Fish Bay dyke, where the outside is a fine-grained dolerite 
with 47.8 per cent silica, while the inner side is a quartz hornblende 
rock with 52.5 per cent silica. These dykes are very wide, 120 to 
150 feet. In smaller dykes the up-and-down current appears to 
have been too rapid for the consolidation to catch the two before the 
completion of the process. Nevertheless, the composite dykes of 
Arran are of the same nature, although of different origin. The 
evidence for this argument afforded by the Quizzyhota laccolite 
will be given in the sequel; it is necessary first to outline the evi- 
dence afforded by the development of single crystals such as anda- 
