Part 15 (1/2)

During the _Primary Epoch_ our globe would appear to have been chiefly appropriated to beings which lived in the waters--above all, to the Crustaceans and Fishes; during the _Secondary Epoch_ Reptiles seem to have been its prevailing inhabitants. Animals of this cla.s.s a.s.sumed astonis.h.i.+ng dimensions, and would seem to have multiplied in a most singular manner; they were, apparently, the kings of the earth. At the same time, however, that the animal kingdom thus developed itself, the vegetation lost much of its importance.

Geologists have agreed among themselves to divide the Secondary epoch into three periods: 1, the _Cretaceous_; 2, the _Jura.s.sic_; 3, the _Tria.s.sic_--a division which it is convenient to adopt.

THE TRIa.s.sIC, OR NEW RED PERIOD.

This period has received the name of Tria.s.sic because the rocks of which it is composed, which are more fully developed in Germany than either in England or France, were called the Trias (or Triple Group), by German writers, from its division into three groups, as follows, in descending order:--

ENGLAND. FRANCE. GERMANY.

Saliferous and gypseous } Marnes irisees Keuper. 1,000 feet.

shales and sandstone }

Wanting { Muschelkalk or Calcaire } Muschelkalk. 600 feet.

{ coquillier }

Sandstone and quartzose } Gres bigarre Bunter-Sandstein.

conglomerate } 1,500 ft.

The following has been shown by Mr. Ed. Hull to be the general succession of the Tria.s.sic formation in the midland and north-western counties of England, where it attains its greatest vertical development, thinning away in the direction of the mouth of the Thames:--

Foreign Equivalents.

-------------------- / NEW RED MARL. Red and grey shales and Keuper. Marnes

marls, sometimes micaceous, irisees.

with beds of rock-salt

and gypsum, containing

_Estheria_ and _Fora-

minifera_ (Ch.e.l.laston).

LOWER KEUPER Thinly-laminated mica- Letten

SANDSTONE. ceous sandstones and Kohle (?) T

marls (waterstones); R

pa.s.sing downwards into I

white, brown, or reddish A

sandstone, with a S

base of calcareous con- S

glomerate or breccia.

I

C< wanting=”” in=”” ...=”” muschelkalk.=”” calcaire=”” england.=””>

S

E

UPPER MOTTLED Soft, bright-red and R

SANDSTONE. variegated sandstone

I

(without pebbles).

E

S

PEBBLE BEDS. Harder reddish-brown

Bunter Gres bigarre, .

sandstones with quartz-

Sandstein. or Gres des

ose pebbles, pa.s.sing > Vosges (in

into conglomerate;

part).

with a base of calca-

reous breccia.

LOWER MOTTLED Soft bright-red and

SANDSTONE. variegated sandstone

(without pebbles). /

P / UPPER PERMIAN. Red marls, with thin- Zechstein.

E

bedded fossiliferous R