Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/470

 large tabular masses of very ferruginous sandstone and in places to concretionary masses of limonite. Its introduction seems often to have been subsequent to the formation of the beds. At some places the same bed presents a stained and an unstained portion, as in the following section* (fig. 10).

Fig. 10. — Section in the Cliff at Walton.

The most remarkable result, however, arising from the presence of iron in these beds is exhibited in a pit near Butley Abbey (fig. 11).

Here the iron has segregated, not in distinct and separate seams or nodules, but in large sections of the sands, throughout which it has produced a pseudomorphous structure affecting the arrangement of the beds themselves, which show on the one hand the concentric layers due to the mineral action, and on the other the lamination due to the bedding. The masses thus affected are as much as from 30 to 40 feet in horizontal diameter, whilst their vertical diameter is but from 3 to 4 feet. The appearance at first sight is as if the beds had been disturbed or reconstructed ; but a closer examination shows that the lines of stratification extend through all the concentric ferruginous rings. Nevertheless the stratification is subordinate to the action of segregation, which has so modified and moulded the beds that the rings or, rather, coats of segregation, when sufficiently consolidated, intersect the slightly consolidated sands and grit just like planes of cleavage in the older rocks, and cause the detached layers to peel off in accordance with the structure superinduced by the presence of the iron, and intersect the bedding at various angles. These concentric rings pass indifferently through beds of sand, grit, and crag, but are cut off sharply or are lost when they come into contact with a seam more highly and entirely ferruginous. It is the most illustrative instance of this kind of action of such magnitude in beds of this class that has come within my knowledge.

From Walton to Aldborough the lower division of the Red Crag abounds in shell-remains, the greater part comminuted, but with many entire and single valves usually placed with their concave side downwards. Some double shells, especially of Mytilus edulis, Astarte, Tellina, Mactra, and Corbula, occur, but they are not common. "With the exception of the old shore at Sutton, with its Mytili and

due to a staining received from encircling beds of Red Crag since removed.
 * Possibly the deep ferruginous colour of the Coralline Crag (g) at Sutton is