THE 
^ "^ 
LIAS (WlfifRSI,,, 
OF 
ENGLAND AND WALES 
(YORKSHIRE EXCEPTED). 
CHAPTER I. 
INTRODUCTION. 
The term Jurassic Extent of the Jurassic Rocks in Britain 
Relations of the Rocks to the Formations above and bcloiv. 
THE foundations of Geological Science are associated more 
closely with the Jurassic Rocks of this country, than with any 
other series of strata. Familiarly known as the Lias and Oolites, 
the main subdivisions of these rocks had been determined and 
their life-history to a large extent ascertained, long before the 
name Jurassic came to be generally applied. To the Jura 
mountains on the borders of France and Switzerland, where the 
" Jura limestone " has been known from time immemorial, we owe 
the name, which was introduced by Von Humboldt. As early 
as 1795 he employed the term "Jura limestone " in a limited 
geological sense, while in 1823 he used the more comprehensive 
names " Jurassiquc " and " Jura formation."* W. D. Conybeare 
had in 1813 recognized the identity of the Jura limestone with the 
Oolitic formations in Englandt ; but not till after the publication 
of Oppel's great work on the " Juraformation " (1856-58), was 
the term Jurassic generally adopted in this country. 
The Jurassic rocks conic to the surface over a large tract of 
Britain. In England they extend from the cliffs between 
Axmouth and Swnnage, on the coasts of Devonshire and Dorset- 
shire, through the Midland counties, to the cliffs and moorlands of 
East Yorkshire. Outlying portions of the rocks occur in West 
Somerset, in Glamorganshire and MonmouthshirCjinWorcestershire, 
Shropshire, Cheshire, and also in Cumberland; while small inlying 
masses appear at the surface in Sussex. In the far north of 
* Alex, de Humboldt, Essai geo^nostiquc sur le gisemeut des Roches, 
pp. 269, 275. (English translation, pp. 36, 359.) 
f He based his correlations on th'j descriptions of Giovanni Arduino (1759) ; 
Eep. Brit. Assoc. for 1832, p. 388. 
K 70859. 
