LAMPLUGH : NOTES ON THE WHITE CHALK OF YORKSHIRE. 75 
of the outcrop of the Chalk-witli-flints is never less than half-a-mile 
in width, and wliere there is a pronounced inland slope of the ground, 
as at Bempton, the outcrop expands to nearly a mile. 
With regard to tlie remaining portion of the series, comprising 
the Lower Chalk and Red Chalk or Hunstanton Limestone (which 
together are equivalent to the Grey Chalk, Chalk Marl, and Upper 
Gault of the South of England), we have precise information in the 
invaluable paper by Mr. W. Hill already referred to. This author 
found the thickness of the Lower Chalk in tlie cliff at Speeton to 
be 132 feet ; and that of the Red Chalk, which forms the base of the 
section, to be 30 feet. 
According to these data, then, the total thickness of the Chalk 
in the vicinity of Flamborough and BridHngton is approximately 
about 1250 feet, made up of the following sub-divisions : — 
Upper Chalk without flints ... ... ... +650 feet. 
Middle Chalk with flints ... 460 „ 
Lower Chalk ... ... ... ... 130 „ 
Red Chalk .. ... . ... ... 30 „ 
Total ... ... .. ... 1270 „ 
This total exceeds by more than one-half the highest previous 
estimate. Even then, if the evidence of the Hornsea boring may be 
trusted, the full thickness attained by the Upper Chalk farther south 
in Holderness has not been recognised, and if allowed for would 
materially increase the above figures. And if for any purpose it 
should hereafter be deemed advisable to attempt to pierce the deposit, 
the facts herein dealt with will require to be borne carefully in mind. 
So far as I am aware, within the limits of the British Islands it 
is only in the Isle of Wight that the Chalk formation has had so 
great a thickness as this assigned to it. 
There, according to the recent work of Messrs. Reid and Strahan,* 
the total depth is over 1750 feet. Near Norwich about 1200 feet 
has been proved ; but elsewhere in the Eastern and Midland Counties, 
the thickness of the deposit is usually estimated at from 500 to 800 
feet. 
* Memoirs of the Geological Survey. Isle of Wight. 2nd ed., p. 75, 
