6 Principles of Geology. 
rocks is confined to no country ; for whether in the new or the old 
world, in continents or in islands, it is so remarkable and so constant, 
that colliers sink deep pits, and miners undertake expensive levels, 
in full confidence that no exception to its generality will affect the 
success of their enterprises. It is not a speculative truth, but a prac- 
tical law of nature, and is, probably, the fact of most extensive in- 
fluence in the whole system of geology. 
the Wernerian school of geology held it to be a universal law of 
structure, and even Cuvier says, ‘ All rocks are stratified.” But 
such expressions are incorrect. How can the term strata be applied 
to basalt, porphyry, and other unconformed masses? That granite is 
sometimes internally stratified, has been asserted,—an appearance I 
-‘hever witnessed,—but every geologist knows abundance of exam- 
ples in which it displays no trace of such astructure. These rocks, 
and some few others, are exceptions to the law of stratification 3 and 
if, as appears probable, their origin is different from that of stratified 
rocks, we need not wonder that they assume other modes of arrange- 
ment. But, neglecting these particular rocks, it is certain that strat- 
ification is the most general phenomenon hitherto discovered by geol- 
ogists. Recognised by observers of different Opinions, and in op- 
posite quarters of the globe, it well deserves to be considered a fan- 
damental doctrine. Let us inquire how these strata are combined 
in the crust of the earth ; for so, perhaps, we may best designate the 
very limited depth to which it has been explored by human enter- 
prise and science. 
To ascertain the manner in which strata are placed in the crust of 
our globe, is certainly the great object of practical geology. The 
first rudiments of this knowledge should be early implanted in the 
mind of the student, by leading him to the contemplation of some 
well-marked natural section. Let him visit the sea-coast, and ob- 
serve for himself whether or not the following proposition is true. 
That, in a local tract, strata are superimposed on one another in a 
certain constant order of suceession, like the leaves of a book. 
Let us take the Yorkshire coast for an example. Gristhorpe cliff 
is Crowned by calcareous sandstone rocks, which lie upon a thick ar- 
gillaceous stratum ; under this is a brown ferruginous rock ; and still 
lower is a thin calcareous layer full of fossils. The same calcareous 
sandstone is found on the top of Red cliff, and it rests in the same 
manner upon the argillaceous stratum, brown rock, and fossil bed. 
{n Scarborough castle hill, the same calcareous sandstone, argillace- 
i 
