LAMPLUGH : NOTES ON THE WHITE CHALK OF YORKSHIRE. 
67 
than 500 feet ;" while the calculations of Barrois,* who estimated a 
depth of 643 feet, were admittedly hased on data acquired during a 
single traverse of the ground. Blake,t who followed, seems to have 
made some careful measurements in the cliffs on the south side of 
Flamborough Head, but did not carry these far enough even to reach 
the base of the Flintless Chalk, and for the lower divisions used figures 
obtained chiefly by calculations of dips and position. By these 
methods he attains a total of 790 feet, which though in excess of any 
of his predecessors' results is still, as I shall be able to show, very 
considerably below the actual thickness of the rocks. 
More recently Mr. ^Y. Hill, J in the very careful study of the 
Lower Chalk already alluded to, has published a detailed measure- 
ment of the beds below the Flinty Chalk, as seen in the cliff near 
Speeton, giving for these beds (including the Red Chalk) a thickness 
of 153 feet, as against the 72 feet allotted to them by Barrois, or the 
100 feet by Blake. My own measurement of this exposure has served 
but to confirm the accuracy of Mr. Hill's figures. 
In the Memoirs of the Geological Survey on the district || no 
original information is given as regards the total thickness of the 
Chalk ; and so far as I am aware, the above quoted are the only 
published statements directly bearing on the subject, though some 
useful data may also be gathered from the late Mr. R. Mortimer's 
paper " On the Flints of the Chalk of Yorkshire,"§; and that of Mr. 
J. R. Mortimer, on " The Chalk Water Supply of Yorkshire."1[ 
The additional information which I now propose to bring forward 
has been almost entirely derived from the detailed measurement of 
the strata as they rise into the cliff on the southern side of Flam- 
borough Head, supplemented by as close an examination as circum- 
stances would permit of the less accessible sections on the northern 
* Barrois C. Recherches sur le Terrain Crdtac^ Sup^rieur, vol. i. , p. 201 . 
M^moires de la Soci^t^ geologique du Nord, 1876. 
t Blake J. F. Proc. Geologists Assoc. , vol. v. , p. 232. 
X Hill W. On the Lower Beds of the Upper Cretaceous Series in Lin- 
colnshire and Yorkshire. Q. J. G. S.. vol. xliv., p. 320 (1888). 
II Memoirs of the Geological Survey. " Oolitic and Cretaceous Rocks 
south of Scarborough" (1880); " Bridlington Bay " (1885); "Th^ country 
between York and Hull" (1886) ; " Driffield" (1886). 
§ Proc. Geologists Assoc., vol. v. p. 344. 
IT Proc. Instit. Civil Engineers, vol. Iv., p. 252. 
