LAMPLUGH : NOTES ON THE WHITE CHALK OF YORKSHIRE. 
71 
we can readily understand the statement that at Hornsea the well- 
sinkers have passed through 800 feet of Flintless Upper Chalk/'' 
With regard to the underlying Chalk-with-fiints, which now 
demands consideration, my data are less adequate. From High 
Stacks I managed with some difficulty to measure the beds north- 
ward as they rise into the cliff as far as Common Hole, on the 
southern side of the Bay of Selwicks, up to which point I found the 
thickness of the Flinty Chalk to be 76 feet. (See Appendix, p. 85). 
But beyond this violent contortions occur, and then a fault, already 
described to this Society.! The fault has a downthrow to the north 
which I estimated (but probably rather overestimated) at 80 feet, 
and its effect is to bring down the Flintless Chalk to the base of the 
cliff on the northern side of Selwicks, and therefore to repeat, in the 
sections beyond, the strata included in the measurement just given ; 
80 that it is only in the chffs north-west of Stottle Bank Nook, quite 
inaccessible, except by boat under favouring conditions of tide and 
weather, that any lower beds appear. 
It has long been my intention to continue the investigation 
from this point by the aid of a boat, but I have never j'et found a 
favourable opportunity. Consequently my knowledge is only such as 
* C. Reid. Survey Mem. Geology of Holderness, p. 6., and p. 141 ; See 
also " On the Flints of the Chalk of Yorkshire," by R. Mortimer, Proc. Geol. 
Assoc., vol. v., p. 34i9 ; Mr. Mortimer supposed, however, that in this boring 
the whole of the Chalk formation was penetrated and its base reached ; on 
this and other grounds he argued that the Flintless Chalk passed laterally 
into the Flinty Chalk, but the field evidence offers no support to this view. 
It is perhaps unsafe to lay much stress on the result of this boring in the 
conflictory state of the evidence with regard to it. All the data, and especially 
the absence of Flint, seem to show that the boring did not reach the Middle 
and Lower Chalk. Yet Mr. W. H. Crofts has favoured me with the following 
note which he recently obtained from the well-sinker : 
"A borehole done in 1862 and 1863, at Hornsea, in a brickyard, for 
Mr. Wade. 
Boulder Clay, sand and gravel ... depth 120 feet 
Thickness of Chalk rock below ... ... 858 , , 
Total depth ... 078 „ 
Below this depth was soft black warp or clay." 
The " black warp or clay seems to have been regarded by the well- 
borers as underlying the Chalk ; but possibly it may have been merely a 
thin marl band interstratified with the Chalk, as seams of this character 
occur at intervals throughout the Yorkshire sections. 
t Lamplugh G. W. " On a Fault in the Chalk, etc." Yorksh. Geol. and 
Polyt. Soc. (1880), vol. vii., p. 242. 
