ocks are developed,
and their general equivalency:

TABULAR VIEW OF THE CAMBRIAN FORMATION.

_Britain._ | _Europe._ | _America._
| |
/a. Tremadoc Slates. | a. Primordial zone | a. Potsdam
| | of Bohemia. | Sandstone.
| b. Lingula Flags. | b. Paradoxides | b. Acadian
Upper < | Schists, Olenus | group of New
Cambrian. | | Schists, and | Brunswick.
| | Dictyonema schists |
\ | of Sweden. |
| |
/a. Longmynd Beds. | a. Fucoidal | Huronian
| | Sandstone of Sweden | Formation?
| b. Llanberis Slates.| b. _Eophyton_ |
| | Sandstone of Sweden.|
Lower < c. Harlech Grits. | |
Cambrian. | d. _Oldhamia_ | |
| Slates of Ireland.| |
| e. Conglomerates and| |
| and Sandstones of | |
| Sutherlandshire? | |
\f. Menevian Beds. | |

Like all the older Palaeozoic deposits, the Cambrian Rocks, though
by no means necessarily what would be called actually "metamorphic,"
have been highly cleaved, and otherwise altered from their original
condition. Owing partly to their indurated state, and partly to
their great antiquity, they are usually found in the heart of
mountainous districts, which have undergone great disturbance,
and have been subjected to an enormous amount of denudation. In
some cases, as in the Longmynd Hills in Shropshire, they form
low rounded elevations, largely covered by pasture, and with few
or no elements of sublimity. In other cases, however, they rise
into bold and rugged mountains, girded by precipitous cliffs.
Industrially, the Cambrian Rocks are of interest, if only for
the reason that the celebrated Welsh slates of Llanberis are
derived from highly-cleaved beds of this age. Taken as a whole,
the Cambrian formation is essentially composed of arenaceous
and muddy sediments, the latter being sometimes red, but more
commonly nearly black in colour. It has often been supposed that
the