66 Mr. Fohn Flower. 
of these, viz., the Stour, the Medway, the Darent, the Mole, 
and the Wey, flow northward into the Thames; and the five 
others, viz., the Arun, the Adur, the Ouse, the Cuckmere, 
and the Ashburn, flow southward direct into the sea. The high 
land in the centre of the Weald gives origin to most of the 
rivers which I have mentioned, but it has also another river, 
the Rother, which cuts through the Hastings sand, and flows 
eastward direct into the sea. In addition to the valleys of 
these rivers there are numerous valleys in the chalk, now dry, 
such as the Merstham and Caterham Valleys and many 
smaller ones, of which I shall have more to say later on. 
The first question which offers itself for solution is how came 
the Weald district to assume the very remarkable form which 
I have described. Numerous theories have been framed to 
answer this question, but it was never, I believe, satisfactorily 
answered until the difficulty was solved by the theory which 
has been adopted by the members of the Geological Survey, 
the result of whose investigations is embodied in one of the 
memoirs of the survey, on ‘‘ The Geology of the Weald,” which 
I have here. 
Stated shortly, the conclusions at which they have arrived 
are as follows: — Omitting the superficial deposits, the 
geological strata which are to be found within the Weald are 
seven in number: (1) the Chalk, which comes at the top, 
several hundred feet thick; and then successively below it (2) 
the Upper Greensand, from o to 8o feet thick; (3) Gault, pro- 
bably from 60 to 150 feet thick; (4) Lower Greensand, from 70 
to 500 feet thick ; (5) Weald Clay, probably from 400 to 1000 
feet thick; (6) Hastings Sands, also several hundred feet thick ; 
and (7) Purbeck beds, probably about 400 feet thick. These 
were probably originally deposited in horizontal beds, one 
below the other, in the order which I have mentioned, and the 
beds now seen on our side of the Channel extended across the 
Channel, which did not then exist at all, and were continuous 
with corresponding beds now to be found inthe north of 
France. 
By one of those alterations in the surface of the earth, 
which were common enough in past times, the strata which 
were in the centre of the Weald were upheaved, and this 
upheaval, which extended across what is now the English 
Channel, and into the north of France, went so far that along 
the line from Horsham to Tunbridge Wells and then south- 
ward to Hastings, the Hastings sand, which in its natural 
position lies below all the other beds of the Weald, except the 
Purbeck beds, was brought to the surface ; and in the north of 
France, where the force of the upheaval seems to have been 
greatest, beds which lie naturally below the Hastings sand 
