UNDERGROUND WATERS OF NORTH-WEST YORKSHIRE. 279 
the river, tlie owner of the land. Mr. J. Hammond, liaving 
kindly given his permission. 
In tlie first place Tarn Dub was sounded and found to be 
only about 18 feet in depth. Now Turn Dub is a circular pond 
of still water, and although a large stream flows out there is 
no disturbance of the surface, no welling up of the water apparent. 
This would lead one to suppose that the j^ool was much deeper 
than is actually the case. So far as could be ascertained by 
drawing the sounding-iron across the pool, the bottom consists 
of large boulders. This led the Committee to suspect that the 
cover was boulder-clay, and that the bottom of Turn Dub 
consisted of boulders, the clayey matrix having been removed 
by the action of the flowing water. 
The boring operations were undertaken with a small set 
of hand boring-rods provided witli an auger bit. 
With this apparatus it was possible to i)rove that the bluish 
alluvial clay was underlain by a material consisting of a somewhat 
sandy brown clay with many large stones, in every way 
similar to the boulder-clay of the neighbourhood, which in some 
])laces can be seen close to the river bank. 
The presence of numerous boulders prevented the boring 
operations being carried more than one or two inches into the 
boulder-clay, so that it was impossible to obtain any definite 
evidence regarding the thickness of the bed. 
Further, although boulder-clay was proved to underlie 
the alluvium on both banks of the Ribble it was impossible 
to obtain evidence of its existence in the river bed, as this consists 
of coarse shingle which could not be penetrated by the light 
hand-boring apparatus employed. 
In order to clear up this matter satisfactorily the services 
of a professional well-sinker were engaged, with the result that 
the existence of boulder-clay below the bed of the river was 
conclusively proved. 
In all seven bore holes \^ere put down, but owing to the 
extremely stony nature of the ground only one of these reached 
the bed-rock. 
This was on the right bank and some 20 feet from the river, 
and the limestone was reached at a depth of eight feet below 
