GABBROS OF EAST SOOKE AND ROCKY POINT. 
43 
izing solutions deposited magnesia and iron, whereas the aplitic 
solutions removed these constituents. They removed lime to a 
small extent, but the aplitic solutions removed much more. They 
added a little silica, but the aplitic solutions added much more, 
and, as the progressively greater silica content toward the centre 
of the aplite veins shows, the proportion deposited grew progress- 
ively greater, and the proportion of lime-iron-magnesia mineral 
progressively less. In their effects on alumina and soda, there was 
less difference between the two solutions. Each removed very 
nearly the same proportion of alumina, and added nearly the 
same proportion of soda, though in the latter case the aplitic 
solutions were slightly more effective. The hornblendizing 
solutions were the more active metasomatic agents, and altered 
the larger volumes of rock. 
Origin and History of the Solutions. 
In the case of a gradually cooling body of magma there 
appears to be no reason to suppose that any sudden discontinuity 
should occur in the processes taking place — in this case in the 
emission of aqueo-igneous solutions. The supposition of grada- 
tional changes in composition, accompanying the gradual decrease 
of temperature that goes on, seems to be more reasonable. Under 
this hypothesis the hornblendizing and aplitizing solutions appear 
only as two phases of one continuous process, the exhalation of 
volatile constituents from the magma, their differences in com- 
position due merely to the natural changes of temperature, and 
other physical conditions, which had taken place in the interval 
between their emission. Such a hypothesis, though incapable 
of direct proof, groups all the observed facts together naturally, 
and affords a satisfactory explanation of the complementary 
nature of the effects of the two types of solutions, as shown on 
Figure 1. 
Under this hypothesis the final aqueous exhalations of the 
magma carried in solution varying amounts of all the different 
component oxides of the gabbro — silica, alumina, iron, magnesia, 
lime, and soda particularly. As these solutions rose and cooled, 
the first reaction, as will be shown, was probably the deposition 
