Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/377



Remains of a pentacrinite, resembling that which is found on the banks of the Severn, near to Pyrton passage.

Fragment of a large compressed and strongly ribbed ammonite.

Slight remains and traces of some unknown pinnated vegetable converted into coal.

Remains of terebratulæ, much resembling T. lacunosa.

Fragment of a large shell of the genus nautilus.

In several places the surface of the limestone strata is exposed for a considerable way, shewing that in many instances they do not consist of a continuous mass, but of an accumulation of columnar distinct concretions, resembling the Giant's Causeway on the coast of Antrim. These concretions are distinctly separated from each other, all their angles are rounded, and there is no regularity in the number of their sides or their dimensions; in some of the strata the whole surface of each concretion consists of that brown crust mentioned above, enveloping a light blue nucleus. This structure of the limestone makes it very easy to work, as it is only necessary to separate the concretions with an iron bar. In this way a great many of the beds near low water mark are worked, and the concretions are brought in paniers on the backs of little horses and asses to the kilns on the top of the cliff. I observed a similar structure in the red rock, but the divisions were much smaller than in the limestone strata. In both instances the appearance is very like that of amass of dried clay or starch. When the strata of limestone are not divided into those columnar concretions, they are generally separated into large irregular shaped masses by joints perpendicular to the stratification, and in many parts they are penetrated in every possible direction by contemporaneous veins of calcareous spar crossing each other like net. work. They seldom exceed a few inches in thickness, and are in general much more slender; the same vein which in the middle is an