THE MIDDLE LIAS OF NORTHAMPTONSHIRE. 
303 
to say, near Kingsthorpe on the north and Kislingbury on the 
west. By joining these two places where the alluvium is 
marked as commencing, we get a line deviating not very 
much from the strike of the beds, such deviation as there is 
being well explained by the preceding remarks. This theory 
is rendered the more probable by the fact that in one of the 
directions the alluvium commences onlv a trifling distance 
eastward of the point where Middle Lias reappears, as shown 
on the geological maps. This is also the position previously 
pointed out for the change in character of the Nen “ fault,” 
lienee it affords additional evidence of the continuity of the 
older-known “fault” with the one more recently discovered. 
I may say here that no evidence of this “fault” has been 
discovered eastward of Northampton, and as the Nen makes 
a decided curve to the north-east soon after passing the 
town, it is unlikely that the two coincide further. 
My readers will now naturally expect that I shall claim a 
less average dip for the Maidstone near Northampton than 
40ft. per mile ; this I propose to do, as it is in accordance 
with the evidence so far obtainable, though I am quite 
indifferent to the result, so far as the water scheme is 
concerned, because whatever increases the area to be filled 
increases the time within which satisfactory results might be 
anticipated, and vice versa. 
The Artesian gradient of the Maidstone is not at present 
known, but considering that in the highly porous New Red 
Sandstone it amounts to oft. per mile, I think it cannot be 
less than 7|ft. per mile* (the dip of the beds eastward of 
Northampton), and therefore, so far as the dumb wells are 
concerned, there could be a head of water of 110ft. at 
Northampton before they would cease to act, or occasion loss.f 
The head of water at the Billing Road well when first made 
was 90ft., or 20ft. less than this. An addition might 
reasonably be made to the gradient for those dumb wells 
situated along the Nen Valley eastward of Northampton, 
because they would be actually more than a mile away from 
the town when only a mile from the line of strike. 
It has been previously stated that coincidently with a rise 
in the water at the Northampton well of between 40ft. and 
* Probably more than this if the material of the bed only were 
considered, but the prevalence of fissures may make it less in some 
directions. •> 
f Height of Nen and river alluvium south of Billing Road pump¬ 
ing station, about 185ft. above sea-level. Height of Marlstone at 
Billing Road well, 75ft. Difference = 110ft. Artesian gradient 
counteracts dip of valley. 
