339 
required, as would overcome the specific gravity of the 
various component parts ; and as the action of a vast deluge 
has been thought to be the only one which could explain 
the phenomena, the term Diluvium has been, till lately, 
generally recognized. 
In no part of Great Britain can this boulder formation 
be studied more effectively than in Yorkshire and Lanca- 
shire, both on account of the large extent of country covered 
by the deposits and the various aspects which they present 
to our view. I shall, therefore, almost entirely confine my 
remarks to instances which occur in these counties; and 
before entering into the discussion of any theory, I will 
endeavour to explain the varied forms which these accumu- 
lations of removed matter assume. For this purpose, I 
shall make three divisions, which I consider to be essentially 
distinct, both as regards their appearance and mode of 
deposition. These are — First, the immense unstratified 
mass of clay, interspersed with boulders and pebbles derived 
from distant rocks, which covers the vale of York, and 
conceals many parts of the regular strata in the east of 
Yorkshire and also in Lancashire. Secondly, the stratified 
deposits of sand and gravel which are frequently super- 
imposed upon the first division. Thirdly, the hillocks and 
terraces of unstratified matter which occur in many of the 
northern valleys.* 
My first division coincides with that termed by Mr. Phillips 
" the proper diluvium," and is accurately described by him 
in the first volume of the " Illustrations of Yorkshire," and 
also in his treatise on Geology in the Cabinet Cyclopsedia." 
At page 20 of the Illustrations," he enters into a minute 
investigation of the diluvium of Holderness, and in the 
* The recent deposits of fresh water origin, ^hich are found in many 
localities, being attributable to totally different causes, are not referred to 
in this inquiry. 
