Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/59

 Rh another pit further to the south on the same line of boundary, but as the mine was destroyed many years ago by the ingress of fresh water, this statement is considerably more doubtful than the former. It may be remarked too, that in sinking for brine a little beyond, or out of the area, on this side, the brine met with is of a very weak and inferior kind, and at a short distance altogether disappears. Appearances leading to the same conclusion of the sudden termination of the body of rock-salt occur on the opposite side of the area marking its extent. In a mine at the northern extremity of the western line of boundary, a shaft situated nearer to this line is fifteen yards deeper than another shaft immediately contiguous, apparently in consequence of the rapid sinking of the rock-salt at this point. In most of the pits on this side, the upper bed of rock is met with at a depth of from thirty to forty yards; yet at Barnton, a mile further to the west, and on the same or a lower level, none was met with in a sinking of one hundred and fifteen yards.

Corresponding appearances have been observed in the body of rock-salt which occurs at Moulton, between Winsford and Northwich, where in two sinkings on the same level, and at the distance of one hundred yards from each other, the difference in the depth at which the rock was found, was nearly twenty yards, a circumstance from which the limitation or going off of the bed at this particular point may reasonably be inferred. As nothing further, however, is ascertained with respect to the extent and direction of this particular body of rock-salt, I merely mention the fact to corroborate the statement given of the limitation of the great beds at Northwich.

Another important observation with respect to the Northwich rock-salt, is, that there seems to be a progressive thinning of the upper bed of salt from NW to SE, or in a direction nearly at right angles to the longitudinal extent of the stratum. Though much