File:The Quarterly journal of the Geological Society of London (12894997703).jpg

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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. .Mar. 9,
the earth's crust

and the work is still going on. It is not a thing
of the past only

but the ocean-bottom, parcelled out like the dry
land into geological districts, is still receiving accessions from animal
debris and insoluble matter suspended in its waters.
The Sections, Figs. 1 & 2, I owe to Messrs. De Verneuil and
Collomb

and they form one - of the results of their very extensive
and methodical investigation into the geology of Spain. They exhibit
the structure of a region, 150 miles long, overspread by great blanks,
which, for our purpose, is sufficiently explained by the sections them-
selves, which are placed here in proof of the importance of our subject.
Fig. 2. — Section of the Sierra Moreno, .Spain), shoiving two great
Blanks in succession (after MM. de Verneuil and Collomb).
N
Villanueva.
Rio
Guadarmena. Alcaraz.
Vianos.
a. Silurian.
b. Red sandstone and variegated clay (Trias).
c. Muschelkalk.
d. Calcaire Grossier.
From an abundant supply of instances of blanks (the indications
of an emerged surface) those described in this memoir have been
selected, as apt to our purpose, and having an ascertained horizon.
They are given in descending order, each successive epoch supplying
the roof of a blank.
II. Instances of Blanks or Gaps.
1 . With a Quaternary Roof. — Throughout by far the greater part
of the extensive countries of Norway, Lapland, Sweden, and Finland,
Quaternary Diluvium and Northern Drift lie directly on Laurentian
and Huronian rocks

little or no deposition having taken place there
(through 25° of longitude and 13° of latitude) during the vast in-
terval of time between that of the contiguous formations. Marks of
denudation are many and powerful here

and though there are
patches of younger strata, they do not require notice from us.
On the opposite coast of North America all this is repeated,
through Labrador and Canada to beyond the Upper Mississippi River,
in a broad belt of rugged land 2000 miles long, where no Mesozoic
nor old Tertiary rocks, loose or fixed, have been met with, though
often looked for. From this block of older metamorphic formations
another broad band of the same antiquity, sprinkled with sand,
gravel, and boulders, runs from Lake Superior into the Arctic Ocean,
through Eupert's Land, for 1500 miles*. Messrs. Foster and Whit-
ney also remark that " Between the Northern Drift of the south
side of Lake Superior and the Devonian there are no deposits, but

Quart. Journ. Geol. Soc. vol. xi. p.