The Map That Changed the World by Simon Winchester

Author:Simon Winchester
Language: eng
Format: epub, mobi
Publisher: HarperCollins
Published: 2009-03-25T16:00:00+00:00

The main outcrop of the Jurassic rocks in England.

The Jurassic rocks here had been given names that were almost as sonorous as the villages on which they lay. The Bridport Sands is perhaps rather prosaic, the Yellow Conglomerate a little less so—but what of the Wild Beds, the Red Bed, the Snuffbox Limestone,* the Forest Marble, the Fuller’s Earth, the White Sponge Limestone, the Scroff and the Zigzag Bed? And if not magical names, then magical appearance: What could be better than the famously extraordinary outcrop, found in a low cliff to the west of the old coastguard station at Langton Herring, which is ten feet thick and made up of nothing less than a solid mass of crushed and flattened specimens of the famous Jurassic oyster, Ostrea acuminata?

The village houses here—most of them ancient, many of them thatched, twined with roses, and huddled into cozy valleys—are generally built of limestone blocks that had been hauled from quarries some miles away, and which could not fairly be said to represent the mishmash of rocks below. This offers a sharp contrast to villages in the Cotswolds farther north, where the underlying Middle Jurassic is an inescapable feature of the architecture overhead. My grandparents had lived for a while in Symondsbury, a pretty village lying a mile or so to the west of my main Jurassic track: Their house was built of Portland stone, an elegant building stone (Saint Paul’s Cathedral; the Ashmolean Museum; much of colonial Williamsburg) that actually comes from near the top of the Upper Jurassic, close to its junction with the Cretaceous. I remember seeing in the old house walls traces of the biggest of all ammonites, the famously lumbering Titanites, which is a marker fossil for the Upper Jurassic; someone also once pointed out part of the internal cast of the shell of another, odder beast: a small, long, conical, spiral-formed snail known as Aptyxiella, which vulgar quarrymen liked to call a Portland Screw.

To the north of Crewkerne, in Somerset, the Middle Jurassic rocks’ lithologies begin to change. I was now leaving the rush and turbulence of the cyclothemic shore, and coming to a point where the seas—shallow but stable—are more oceanic than coastal, less disturbed, less turbid. The limestones become purer and thicker and more resistant—both more resistant than the rocks in Dorset that are of the same age and, more significantly, more resistant than the rocks in Somerset, Gloucestershire, and Oxfordshire that are younger, and lie on top of them. Because of this the outcrop of the Middle Jurassic everywhere north of the Dorset-Somerset boundary is marked by a sudden, steep hill: As I traveled farther and farther north, so this hill, and the very prominent edge where it rises up and away from the softer rocks below, becomes ever steeper, more and more evident, more and more obvious.

Small wonder that William Smith found the area around Bath the most congenial for his studies. Not only was it an attractive town, jammed with interesting personalities

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.