B. Thompson—Clay Beds by the Ouse. 27 
Next let us consider the beds near to Olney. The greater part of 
the town of Olney is supplied with water by shallow wells in the Ouse 
Valley gravel, but in the southern part of the town, between the 
Market Place and the river, and south-westward, on the road to 
Weston Underwood, the wells are from 60 to 80 feet deep in Lias 
Clay. It has been assumed that the difference in depth is due to an 
unconformity between the Upper Lias and the Upper Estuarine beds.' 
Personally I can see no reason whatever for this assumption, for no 
surface irregularity in the upper beds, not relied upon for water, 
could possibly alter the level above ordnance datum at which water is 
found. Wells are not all started at the same level, and if they were 
some might have a deeper sump than others. However, here is some 
evidence “bearing upon this question of unconformity and other points. 
At the extreme south-eastern end of Olney, and on the south side 
of the road, there used to be a brickyard (the excavation can still 
be seen). Mr. Cameron reports? that the beds worked were yellow and 
blue clay, and that there was a sand bed one foot thick at the depth 
of 8 feet from the surface. It is suggested that this sand bed may 
perhaps be a representative of the Northampton Beds (see remarks 
later). 
Not many yards eastward of this disused brickyard a well has been 
made for the supply of some cottages, and the report given to me 
of this well was that it was 80 feet deep, all in blue clay, and that 
they got water from a black rock 2 feet thick, below which blue clay 
was again met with; the water rose 50 feet from the rock. 
A little westward of the old brickyard, just about where the hill 
begins to rise sharply, a small excavation made in levelling for 
a hayrick exposes about 8 feet of a light-coloured oyster marl. 
Seven feet below the top of this, water flows from the bank. 
The levels hereabouts are as follows :— 
Above O.D. 
Water-level in the river ade 163 feet. 
Level of spring trom marl (base of Upper Estuarine beds Ness 1S 2s 
Well-top at houses . cis a Rap US vaates 
Top of clay at old bricky ard... os certainly near to SZ. 
Further along the very steep cliff bordering the Ouse Valley 
between Olney and Weston Underwood, limestone or marl was 
found at various places between the levels of 211 feet O.D. and 
229 feet O.D. So far as it goes this is satisfactory, for without 
correction it would mean Upper Estuarine beds not more than 
211—182 = 29 feet thick and Great Oolite limestone not less than 
18 feet. The highest exposure of limestone coincided with the fence, 
but the roadway is six feet higher, and obviously at least this amount 
must be added to the limestone, making it 24 feet, so that not much 
need be added to it below. 
If we consider that the base of the Upper Estuarine beds at Stoke 
Goldington is correctly indicated by the level 245—27=218 feet O.D., 
and at Olney by 182 feet O.D., then there is a dip from the former 
locality to the latter of 86 feet, or 93 feet per mile, and this same dip 
1 Thid. 
2 Thid., p. 394. 
