178 
THE MIDDLE LIAS OF NORTHAMPTONSHIRE. 
is the little piece of adverse evidence referred to a page or 
two back. The micaceous clay—see Section, p. 75, Vol IX. 
—out of the well seemed about as I expected to find it, but 
quite dry, whereas the bed just below yielded water under 
considerable pressure. From the condition of the fossils, 
too. I do not think much water had passed through this bed. 
About this time attention was directed by the opponents 
of this scheme to a fresh instance of the Marlstone being 
found without water. It was a well sunk at Messrs. P. 
Phipps and Co.’s Brewery. On investigation I was surprised 
to find that a large amount of water was being obtained 
from the well ; it issued from cracks in the rock along two 
headings, and the amount of water was increasing rather 
than diminishing, owing probably to the development of 
more definite channels. I was still more surprised to find 
that the rock was not the Rock-bed , but the lower water¬ 
bearing bed. The evidence on this latter point was quite 
definite, the common Rock-bed fossils were entirely absent, 
and those characteristic of lower beds present; furthermore, 
Mr. T. Phipps informed me that the water was quite differ¬ 
ent to that supplied to them by the town waterworks. 
This same spring was also met with at Gayton (see p. 74, 
Yol. IX.) 
It seems, therefore, practically certain that the lower 
spring might have been found at the Billing Road Well had 
it been sought for, and from its position, on the northern 
side of the Nen fault, it might be expected to yield a supply 
of water greater than that of any of the other places where 
it had been tapped in the neighbourhood. The expense con¬ 
nected with deepening the well, probably less than 25 feet, 
would have been much less than that incurred in obtaining 
other small temporary supplies. 
It must at least then be conceded that the lower part of 
the Middle Lias under Northampton is not impervious, 
although it may not be as porous as the Rock-bed. 
It must be borne in mind that when water gets into a 
porous bed in which there are no open fissures, there imme¬ 
diately commences a struggle between capillarity and gravity, 
and no water will flow till the capillary-holding power of 
the rock is satisfied ; afterwards the flow of water depends 
upon the size of the interspaces between the particles, which 
interspaces are, of course, proportional to the size of the 
particles. A stiff clay consists of such small particles that 
the interspaces are minute enough to retain all the water 
that can get in, consequently, when a clay is once thoroughly 
wetted, no more water can pass downwards through it. 
