THE MIDDLE LIAS OF NORTHAMPTONSHIRE. 
292 
movement took place that resulted in the southern area 
becoming highest at Northampton and lowest at Weedon. 
With regard to the second statement (b), I would say that 
the presence of a “fault” coincident for nearly 11 miles 
with the Nen valley cannot be regarded as the result of chance, 
Moreover, the arrangement is quite in accordance with state¬ 
ments previously made with respect to the origin of “ faults” 
and valleys (see page 231, Vol. X.). 
We are now in a position to define, with a considerable 
degree of probability, two of the boundaries of the area that 
might be filled with water, for two lines may be drawn on a 
map from the position of Northampton, one running west¬ 
ward along the Nen valley, representing the boundary of the 
southern area, which can neither give water to nor take water 
from the northern area ; and the other at an angle of 125° 
with this, i.e., in the direction of strike of the bed, on one side 
of which the Maidstone is full and the other requires filling. 
I candidly admit my inability, at present, to even approxi¬ 
mately define the other boundary, as it depends upon the 
inclination of the bed, and the artesian gradient, neither of 
which are known with a sufficient degree of certainty. Of 
course, dumb wells constructed anvwhere between the lines 
just referred to, and within the outer boundary of the 
Marlstone outcrop, could help to fill up the bed. Hence 
a previous suggestion of a radius of 15 miles for such wells, 
but it does not follow that the bed could ever be filled up to 
their position. 
What is known about the inclination of the Marlstone I 
will now give, more for future reference than present use. 
The Marlstone at Northampton is 75ft. above sea-level, at 
Daventry 490ft., a fall of 415ft. in Ilf miles — 35|ft. per 
mile, nearlv. 
At Naseby, about 11 miles from Daventry on the line 
of strike, the Marlstone is said to be 500ft. above sea-level, a 
fall of 425ft, in 12 miles = 35jft. per mile, nearly. 
The true dip deduced by taking a line at right angles to 
that joining Daventry and Naseby and passing through North¬ 
ampton, gives 40ft. per mile. 
These are satisfactory and consistent enough if taken by 
themselves, but do not agree with the inclination deduced in 
another direction in another way. It has been remarked aud 
explained in Part 1. that where streams run over clay beds, 
the beds have the same dip or inclination as the valleys in 
which they are exposed, it thus seemed probable that we 
might ascertain the dip of the Middle Lias by the fall of the 
river. 
