THE Ui;ol,0C5IST. 
the circumambient pasty rock, and, laminating, streaking, and con- 
torting it in the " squeeze and jam" of its intermural expression, pro- 
duced the ribboned-structui'ed mica-schist and gneiss.* 
When we regard the extensive areas still exposed of the old gneiss 
and similar-aged rocks in various parts of the world, and which pro- 
bably have remained uncovered by any sedimentary deposit whatever 
from the first hour that the golden sun tinged their brine-washed 
crowns to the present play of his cheering rays upon their grey and 
barren fronts, we may well ask if those oldest gneissic rocks have 
thus been formed ? 
We must, however, look upon these granitoid and gneissic founda- 
tions as the buttresses, denuded and weathered out in the lapse of 
incomprehensible ages from the originally circumambient beds, and 
exposed in this way to our view, rather than as dykes of molten 
matter, forced completely through open fissures into the upper air. 
We have alluded to the different ages of granite-formation and their 
outbursts by the influence of internal heat on successive sedimentary 
floors; may we thence look to find any difi"erence of composition, 
marking the difterence of the age in which each was generated and 
irrupted ? Mr. Sterry Huut has done something towards this know- 
ledge. He has pointed out that the oldest granite contains most 
soda, and that the quantity of that alkali diminishes sensibly in the 
several granitic masses in proportion to the proximity of their epoch 
of formation to our times. Hence this proportional quantity of one 
chemical ingredient may some day be made subservient to an approxi- 
mate registration of geological time upon the great chronological dial. 
As the first granites, or gneissic rocks, were worn down into sub- 
marine sediments, to be afterwards changed in the progress of natural 
phenomena into newer granites and metamorphic rocks, fi'om those 
sedimentary materials the primeval oceans dissolved out and accumu- 
lated much of that soluble substance ; and so, those regenerated and 
less alkaline granitoid rocks being again worn down, their sediments 
were also in the lajjse of time formed into newer granites and schists 
with a still less quantity of alkaline matter. 
But let us go back to the old gneiss and the law of upheaval by 
• See Mr. Scrope's paper in The Geologist, vol. i. page 361. 
' t 
