which the cavities of these rocks were once filled. From this cause the promontory, on which Hartlepool stands, is rapidly crumbling away.
It is well ascertained that the magnesian limestone of this district, as is the case with that of Derbyshire and Yorkshire, rests upon the coal-measures. No coal mine however has yet been won in Northumberland or Durham, by sinking a shaft through the limestone, although the workings of some collieries situated on its western boundary have been carried underneath it. It is therefore a matter of great importance to those who have royalties within its limits to know under what thickness of limestone the coal measures are buried; whether after passing under the limestone they continue to dip at the same angle as before, and whether the quality or thickness of the coal-seams is then altered.
I have not been able to ascertain what is the total thickness of the limestone; but at Hart, near to Hartlepool, a bore—hole was made in it to the depth of 52 fathoms, without penetrating through it. This spirited undertaking was then frustrated from the perforation being filled with sand and water. At Pallion, a little to the west of Sunderland, the limestone was only 12 fathoms thick, below which the coal measures were bored through to the depth of 140 fathoms without finding a coal seam worth working.
Along the coast of Durham from Shields to Hartlepool the limestone strata dip to the south-east. At Chapted main near South Shields, the coal measures, although approaching the limestone, rise towards the sea, in conformity to their direction on the north side of the Tyne; but at Painshaw, New bottle, Rainton, &c. they dip to the south-east, the limestone being there protruded into the Coal-field beyond the prolongation of that line, from which the coal measures that are without covering begin to rise in an eastern
