Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/492

 "diluvial sand with boulders." The exposures of the beds in question over this area are usually of a very limited character, and are almost entirely confined to such accidental openings as stone-pits and brickyards, while nowhere does any such key to the relations of the beds occur as that which is afforded by the grand cliff-section of Yorkshire. Owing to these causes the geologists of North Germany have been reduced, in the classification of their Neocomian strata, to rely, almost solely, upon palaeontological evidence, especially upon that obtained by comparison with the typical beds of the same age in Switzerland. An examination of the results thus arrived at, side by side with those obtained by the study of the very similar and much more favourably exposed beds of the North of England, while it, on the whole, confirms the views now generally held by Continental geologists, yet suggests some modifications of those views, of considerable interest and importance.

It is not my intention to attempt any thing like a general description of the Neocomian formation in Northern Germany ; this subject has been already most admirably treated in the works of Fr. Ad. Romer, Geinitz, Ferd. Romer, Beyrich, Ewald, and especially of von Strombeck. What I propose is, to show the relations of the various strata of this age in Northern Europe with those in the northern parts of this country. To qualify myself for this task I have visited nearly all the most typical sections in North-western Germany, and have examined all the public and many of the private collections of fossils in that district ; and it is with much pleasure that I take the present opportunity of acknowledging the great amount of kind assistance which I received from several distinguished German geologists, among whom I may especially mention M. von Strombeck, of Brunswick, M. Hermann Romer, of Hildesheim, and M. Witte, of Hanover.

1. Heligoland. — "We have seen that at Speeton the Neocomian strata, even before their full emergence from beneath the overlapping Chalk strata, are cut off by the denuding action of the North Sea. Intermediate between this section and those of North Germany, an important and extremely interesting link is afforded by the beds exposed in the little island of Heligoland, which is rapidly wasting away beneath the waves of the German Ocean. The strata in question are exposed, not in the cliffs of the present island, but in certain banks, visible only at low water, about a small islet which is said to have been separated from the main island within historical times. The beds appear to be inclined at a considerable angle ; and their succession is as follows : —

(1) White Chalk, containing a large series of fossils, agreeing precisely with those of the Lower Chalk of Yorkshire and Lincolnshire.

(2) Variable beds of " rust-yellow and yellowish red chalk or limestone," some of which become more or less sandy, containing Belemnites minimus, List.

(3) Blackish-blue pyritous clays (called Tock), containing many fossils mineralized by iron pyrites.

(4) Beds with Oxfordian fossils, followed by others with Lias fossils.