The Tertiary district thus appears, on a general view, to be divided naturally into four portions by lines running nearly north and south, the former line passing immediately south, and the latter east of London, which stands at the south-east corner of the north-western division, and consequently it must not be viewed as the centre of one large and unbroken area, so far as the Tertiary strata are concerned.
[CHAPTER II.]
THE NEW RED SANDSTONE.
This formation has been already alluded to at pp. [5] and [8]; it is, next to the chalk and lower greensand, the most extensive source of water supply from wells we have in England, and although the two formations mentioned occupy a larger area, yet, owing to geographical position, the new red sandstone receives a more considerable quantity of rainfall, and, owing to the comparative scarceness of carbonate of lime, yields softer water.
The new red sandstone is called on the Continent “the Trias,” as in Germany and parts of France it presents a distinct threefold division. Although the names of each of the divisions are commonly used, they are in themselves local and unessential, as the same exact relations between them do not occur in other remote parts of Europe or in England, and are not to be looked for in distant continents. The names of the divisions and their English equivalents are:
1. Keuper, or red marls.
2. Muschelkalk, or shell limestones (not found in this country).
3. Bunter sandstone, or variegated sandstone.
The strata consist in general of red, mottled, purple, or yellowish sandstones and marls, with beds of rock-salt, gypsum pebbles, and conglomerate.