48 
DAVIS ; CONTORTIONS AT FLAMBOROUGH. 
(Geology for Students, 1876, p. 375,) enters into the relative merits 
of this question with considerable detail. If a horizontal bed of 
chalk be subjected to pressure applied vertically from below so as to 
produce a series of anticlinals and synclinals, it is evident that the 
bed will become longer if bent into a series of curves than it was 
when simply straight. If, on the other hand the pressure has been 
applied laterally, the bed of chalk will be compressed or squeezed 
into a smaller compass. Prof. Green says : — " Where rocks have 
been sharply bent into folds which follow one another in rapid 
succession, they would have to be pulled out to many times their 
original length to bring them into their present shape. Even 
supposing rocks as extensible as india-rubber, increase in length 
must be attended by a corresponding decrease in thickness, and 
therefore a group of rocks, when sharply folded, ought to appear to 
be more thinly bedded than in their undisturbed position. But if we 
take a group of rocks which lie undisturbed at one spot, and one 
violently contorted at another, we do not find the beds thinner at the 
latter than at the former. In reality, however, rocks are only 
slightly extensible, and it is utterly out of the question to suppose 
that the^^ could possibly have been dragged out to the extent 
necessary to bring them into their present form by vertical upthrust. 
No such difficulty accompanies the squeezing hypothesis : a band 
of rock, which when horizontal was, say, a mile long, is forced to 
occupy a smaller space, say, three-quarters-of-a-mile, and the only 
way in which this could be done is by puckering it up into folds." 
It is very probable that the foldings or contortions were 
produced, not only at a period long subsequent to that of their 
deposition, but also after the accumulation of a considerable mass of 
superincumbent matter, so that when the operations were in progress 
the contorted chalk was buried beneath a great thickness of strata. 
This will be evident if it be considered that a large amount of 
material has been removed from the upper surface of the section 
now photographed. The upper portion of the arches has been to a 
large extent removed by denudation, and there is a strong probability 
that at least some hundreds of feet of chalk have been carried away 
by this means. Experiments conducted by Prof. L. C. Miall and 
