m 
PREFACE, 
IN pursuance of the scheme for completing the Memoir* of the 
Geological Survey by the publication of stratigraphies) mono- 
graphs of the difl'erent geological formations of the British Isles, 
the task of describing the Jurassic system south of the Humber 
was entrusted to Mr. H. B. Woodward. The present volume, 
coming after the two by Mr, Fox-Strangways issued last year, 
forms the third volume of the Jurassic Monograph, and is the first 
instalment of Mr. Woodward's work. It is devoted to a detailed 
account of the Lias. . . . 
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Following out the general plan adopted for these Memoir*, 
Mr. Woodward has endeavoured to summarise our knowledge of 
the different subdivisions tf the Lias, with especial reference to 
their stratigraphical variations and their economic products. He 
has availed himself not only of the information gathered by the 
officers of the Survey, but of the voluminous Liassic literature 
which has been published in this country, so as to present a com- 
pendium of what is at present, known regarding the subject. 
In tracing the labours of those who preceded the detailed 
mapping of the Survey, we may note with some interest that an 
original sketch-survey, on the one-inch Ordnance maps, was made 
by William Lonsdale between 1827 and 1836 over a great part of 
the area described in the present, volume. This early pioneer in 
British Geology, following the outlines first given by William 
Smith, and proceeding from near Bath across the Cotteswold dis- 
trict, made his way by a series of oblique traverses through the 
Midland Counties to the Humber. H. E. Strickland also 
mapped portions of the Lias and New Red Sandstone on the 
borders of Gloucestershire, Worcestershire, and Warwickshire 
between the years 1834 and 1837. Shortly afterwards De la 
Beche, in the early days of the Geological Survey, pushed his way 
from Cornwall and Devon into Somerset and Dorset, and before 
the year 1839 had begun the official mapping of the Jurassic rocks. 
This work was carried on by II. W. Bristow, and partly by 
W. T. Aveline, in Dorset, Wilts, and Somerset, and by Ramsay in 
Gloucestershire, followed afterwards by E. Hull, H. H. Howell. 
H. Bauerman, R. Trench, T. R. Polwhele, and A. H. Green, by 
E 70859, 750. 8/93. Wt, 23920. a 2 
