13 
colliery at Rawmarsh ; pointing out the changes in the 
depth of the coal at these places, and in the direction of the 
water levels ; that while the general direction of the water 
levels, both to the North and South of the valley of the Don, 
was from N.W. to S.E., yet, in the valley, for five miles, the 
direction of the water levels was at right angles to their ge- 
neral course, viz., from N.E. to S.W. 
Mr. Hartop illustrated his remarks by a map of his own, 
constructed some years ago, for the purpose of laying down 
the water levels of the different collieries, and he thought it 
would be very useful if this were made a leading feature in 
geological maps, in mineral districts. 
Mr. Morton said, the Society had several times been 
favoured with explanations of the geology of the Don valley. 
Indeed, it had become a sort of standing subject, but unfor- 
tunately there were not two explanations alike. The 
arguments advanced to-day by Mr. Thorp to prove the 
existence of a synclinal axis were certainly novel, and, he 
thought, philosophical, and in accordance with facts. Mr. 
Morton's own observations of the geological structure of the 
country between Leeds and Chesterfield, led him to coincide 
with Mr. Thorp's views. From Billingley to Leeds, the 
strata rise to the North and North- West, but from Rother- 
ham to Chesterfield they rise to the Southward ; and the 
inference is, that the measures between Billingley and 
Rotherham lie in the bottom of a deep hollow or depression, 
which, in fact, is Mr. Thorp's synclinal axis. Mr. 
Hartop, on former occasions, had endeavoured to shew 
that a lateral movement of the strata had taken place 
towards the East ; but the evidence was not sufficiently 
strong to satisfy him (Mr. Morton) that such was the case. 
From the commencement of the Society's discussions on 
this subject, Mr. Morton had always considered that the 
geological phenomena of the Don valley could be explained 
by the supposed intervention of a large fault, which had 
