Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/106

 94 nature of the rocks of a district, but likewise the general disposition of the strata, and their relation in point of position to the surrounding country) one of the most interesting undoubtedly is that of flint in chalk, which is subordinate to the secondary formation in the great and generally admitted division of rocks into primitive, transition, and secondary.

Whatever be the country, where the formation of flint in chalk or marl occurs, it is worthy of remark:

I. That it occupies a considerable extent.

II. That it belongs to flat countries stratiform or alluvial and what appears to me a more striking circumstance is, that as far as I know, it is to be met with chiefly on the skirt of some great chain of mountains at some distance; as if it made one of the links of a complete system of formations. Thus, in France, it prevails on the skirt of the western boundary of Mount Jura, extending in a direction from S. E. to N. W. and covering a space of at least two hundred and ten miles long, by about one hundred and broad. In Poland, on the borders of the chain of the mountains, from the shores of the Baltic, comprehending the plains of the Pilica, of the Bug, and of the Vistula, as far as the first heights where these rivers have their source. In England, to the east of the mountainous part of Devonshire and Cornwall, and stretching across to the German ocean. This formation is also found in Ireland, Saxony, Spain; Denmark, and Sweden; but I do not sufficiently know in what particular situations, to enable me to notice them in a less general manner.

From the nearly exact correspondence of the meridians under