70 THE STEUCTUEE OF THE OULLY, DUEDHAM DOWNS. 
hypothesis. The only objection to it is that such a disloca- 
tion must be very rare. I do not recollect having read of 
anything similar. But the conditions were very peculiar. 
Although the above may serve to explain the presence of a 
vertical series of Middle Limestone Shales in a notch in the 
Gully Oolite, we have still to account for the horizontal, and, 
lower, anticlinal arrangement of the superjacent cream- 
coloured shales. 
Now the development of these is very remarkable. It will 
be remembered that they lie against the oolite walls of the 
notch sometimes nearly or quite conformably, but usually at 
an angle, and that there is no crushing at the junction ; the 
shale ends abruptly against the massive rock, without 
slickensides. 
Secondly, these horizontal and anticlinal shales have been 
profoundly altered, and made cream-coloured, by the action 
of percolating water. 
Thirdly, there is no evidence either of erosion where they 
join the vertical beds, or of passage of the one stratification, 
by a complicated bend, into the other. Rather the horizontal 
lamination has been superinduced on the vertical, just as we 
may find slaty cleavage superinduced on shaly bedding. 
We know that in Liassic times the top of the great Car- 
boniferous anticline had been cut off, and the Liassic sea 
swept over the Downs. It so chanced that the top of the 
notch in the Gully Oolite was exposed to this sea, filled as it 
of course was with Middle Limestone Shales. Now as these 
shales were vertical in the notch, they were extremely per- 
meable. But the water could far less readily soak away 
through the shelf of Gully Oolite below them, which is very 
massive. The only escape was, therefore, along the layer of 
shale next overlying the oolite, which had a narrow com- 
munication with the vertical series over the lip of the notch. 
The consequence of this arrangement must necessarily have 
