Explanation o f Letters and Figures used in the references to
unstratified and crystalline Rocks in Plate 1.
a. Granite. b. Sienite. c. Porphyry,
d. Greenstone. e. Serpentine. f. Basalt, or Trap,
g. Trachyte. h. Products of Extinct Volcanos. :
i. Products of Active Volcanos.
a. 1.—a. 3. Mountains of Granite, raised into lofty ridges,
from beneath Gneiss and Primary Slates,
a. 4. Granite intermixed with Gneiss,
a. 5.—a. 8. Granite, subjacent to stratified rocks of all
ages, and intersected by volcanic rocks,
a. 9. Granite Veins, intersecting Granite, Gneiss, and
primary Slate.
a. 10. Granite Vein, intersecting Primary and Transition
rocks, and forming overlying masses at the surface.
a. 11. Granite Vein intersecting Secondary strata, and
overlying Chalk.*
b. Dykes of Sienite.
b. 1. Overlying masses of Sienite.
c. Dykes of Porphyry.
c. i. Overlying masses of Porphyry.
d. Dykes of ancient Greenstone.
d. 1. Overlying masses of the same. The Rocks represented
by d. and e. often pass into one another.
e. Dykes of Serpentine.
e. 1. Overlying masses of Serpentine.
f. Dykes and intruded subterraneous masses of Basalt,
f. 1. to f. 7. Masses of Basalt protruded through, and
overlying strata of various ages.
* In the locality quoted in the Explanation o f Plates, Yol. II. p.
5, the Granite which comes to the surface over the Chalk, is not
covered by Tertiary deposits, as represented in our section, PI. 1.
fi 8. Basaltiform products of Modern Volcanos.
g. Trachyte forming Dykes.
g. 1. Trachyte forming overlying Domes. (Puy deDome.)
h. 1. h. 2. Lava of extinct Volcanos, forming undisturbed
Cones. (Auvergne.)
i. —i. 5. Lava, Scoriae, and Craters of active Volcanos.
(i. 1.—i. 4. Etna. 1—5. Stromboli.)
k.—k. 24. Metalliferous Veins.
k. 15'. Lateral expansions of Veins into metalliferous
cavities, called by the Miners Pipe Veins, or Flats.
l. —1. 7. Faults, or fractures and dislocations of the strata.
The continuity of stratified Rocks is always interrupted,
and their level more or less changed on the
opposite sides of a fault.
It is unnecessary here to give detailed descriptions of the
28 divisions of the Stratified Rocks represented in our Section.
Their usual Order of Succession and Names, are expressed
in their respective places, and detailed descriptions
of their several characters may be found in all good Treatises
on Geology.
The leading Groups of Formations are united by colours,
marking their separation from the adjacent groups; and the
same colours are repeated, in the headings above the figures
of Plants and Animals, that characterize the several series
of Formations, to shew the extent of the strata over which
the Organic Remains of each Group are respectively distributed.
The Formations of Peat Bogs and Calcareous Tufa are
of too local a nature to be included in. the series of stratified
Rocks represented in this Section; although they sometimes
operate locally to a considerable extent, in adding
permanent and solid matter to the surface of the Globe.