234 
THE MIDDLE LIAS OF NORTHAMPTONSHIRE. 
We will assume for a moment that the depth of 210 feet 
for the Marlstone is correct, then the section would be about 
as below :— 
Great Oolite j 
FEET. 
Inferior Oolite > 
Upper Lias ) 
... 210 
Middle Lias 
... 21 (Spinney Well Estimate.*) 
Lower Lias 
... 629 
Sandstones 
... 80 
Red Marl... 
... 12 
Conglomerate 
... 15 
967 
The notes respecting the last three beds are said to have 
been made by Dr. William Smith, F.R.S., F.G.S., and 
Mr. Sharp, in whose possession they were, appears to have 
quoted the thicknesses of the upper one and the sum of the 
beds above it differently in two separate papers.! In the 
earlier one, he says, the Lower Lias was pierced at a depth of 
860 feet, and 80 feet of Sandstones met with ; in the later one 
880 feet and 60 feet are the thicknesses quoted for the same 
things. It may be that the second figures are a correction of 
the earlier ones, and certainly the thickness of the Sand¬ 
stones agrees better with the Spinney Well record; neverthe¬ 
less, I have preferred to retain the earlier ones, although less 
favourable to the particular contention founded upon them. 
Now the total depth of the Kingsthorpe shaft is no doubt 
correct, the thicknesses of the lowest three beds are probably 
so; but if we accept the other figures given, then, (1) The 
Lower Lias must have a thickness of 629 feet, that is, 88 feet 
more than at the Spinney Well, about a mile away ; (2) The 
Marlstone Rock-bed is 164 feet above sea-level, that is, 89 feet 
higher than at Northampton, and 51 feet higher than at the 
Spinney Well; (3) The thickness of 210 feet for the Great 
Oolite, Inferior Oolite, and Upper Lias is less than might be 
expected. 
Considering that after the termination of the Carboniferous 
land period the inequalities of surface then produced were 
largely obliterated by deposition of the Permian or Trias, 
or both, and that the highest parts of the Carboniferous 
limestone in this very district were covered by the latter, it is 
* “The Range of the Palaeozoic Rocks beneath Northampton,” by 
Henry J. Eunson, Esq., F.G.S. Q.J.G.S., August, 1884. 
f “ The Oolites of Northamptonshire,” Part I. Q.J.G.S., August, 
1870. “Note on a Futile Search for Coal near Northampton,” Geol. 
Mag., Yol. VIII., p. 505, 1871. 
