and the Nature of the Liquidity of Lavas. 201 
I would ask of geologists to consider whether such a mode of 
protrusion of the laminated crystalline rocks, and of the lateral 
replication of the more earthy schists and marine strata, as is 
here suggested, does not accord with the general facts known 
respecting their position? Let me take two descriptions of the 
general position of the crystalline rocks from two writers of ex- 
perience, judgement, and wholly impartial character, as respects 
the theory here indicated. Mr. Evan Hopkins* gives as the 
results of his extensive mining experience in the Andes and else- 
where, “that the great base [of all mountain-chains] is below 
more or less granitic, strongly saturated with mineral waters, 
and that this passes upwards by insensible gradations from a 
crystalline homogeneous compound into a laminated rock, such 
as gneiss, and still higher up into schists in vertical planes ; the 
peculiar varieties of the higher rocks depending on the mineral 
character of the ‘ parent rock’ below; the schistose rocks form- 
ing, in short, the external terminations of the great universal 
crystalline base,’—that is to say (as I would phrase it), the 
squeezed out, and therefore laminated, upper and lateral portions 
of the inferior crystalline mass. 
Mr. Ruskin, in his recently published volume, having closely 
examined the structure of the Alps with the eye of a geologist 
no less than of a painter, but certainly without any theory to 
support, declares that the central axes of “ irregular crystallines ”’ 
(as he calls the granitic rocks) uniformly graduate on either side 
into the foliated or “‘slaty crystallines,” 7. e. into gneiss and 
ultimately mica- and chlorite-schists. 
One point observed in the structure of the Alps and many 
other mountain-chains I may notice before I conclude, namely 
the occasional dip of the elevated strata towards the central axis 
of extruded crystalline rock, producing a synclinal instead of an 
anticlinal ridge. Another section copied loosely in the frontis- 
piece to my work on volcanoes, from Von Buch’s paper on the 
Tyrol, may show the mode in which I conceive this to have 
occurred through the injection of a mass of crystalline matter 
into a wedge-shaped fissure, opening downwards ; such as must 
have frequently occurred among the fractures of the overlying 
strata—giving occasion in some cases to the further rise of the 
heated and intumescent matter into the hollow between the outer 
slopes of the synclinal valley. It would indeed accord with the 
theory suggested above, if such dykes or extravasations at syn- 
clinal axes were found to alternate frequently with the elevated an- 
ticlinal axes, for the cracks formed in indurated beds of overlying 
* Quart. Journ. Geol. Soe. vol. xi. p. 144. 
