Of the modern subsidences, which are of three kinds, we have no documentary evidence prior to 1777, and the earliest distinct record belongs to the year 1790. From that time to the present day this class of sinking has continued to increase in extent year by year. In 1790 the sinking portion along the Witton Brook was recorded as being 130 yds. long by 90 yds. wide. In 1837, the subsidence had obtained an area of 1,230 yds. long by 130 yds. wide. In 1811, about 20 statute acres in Witton commenced sinking, and in the ensuing thirty-three years some portions of this area had sunk 24 ft. In 1880, the piece of water called the Top of the Brook had subsided over an area of 4,370 ft. by 1,470 ft., and in the same year it was estimated that no less than 2,700 acres of land in Northwich and Winsford were inundated. These modern subsidences usually consist of funnel-shaped holes caused by the falling-in of top-rock mines, and of trough-shaped hollows which cannot be connected with rock-salt mining, and are frequently found in places far removed from the localities of the old workings. Of two dozen subsidences, two are nearly four miles distant from the nearest old workings or from the brine shafts, fifteen are upwards of two miles, and only one is less than a mile from either a mine or a pumping station. The subsidences could not be caused by volcanic action or the shock of earthquakes, as nothing of the kind has occurred in the districts, and it is impossible to explain them by the action of natural brine springs running to waste in the brooks or rivers, because it is known that no such springs now exist, while evidence accumulated from all parts of the world confirms the conclusion that where brine springs escape into the streams, no subsidence has ever occurred. Yet it is evident in Cheshire that some subterranean denudation must be taking place which is removing portions of the lower strata and allowing the super-incumbent earths to sink into the excavations thus made. Many theories have been advanced to explain the phenomena, but even those people whose interests have caused them to seek for alternative causes must realize that it can only be attributed to the simple and most obvious agency. When the number of brine pits was multiplied and the natural springs of a weak solution of salt decreased in volume, it was necessary to sink down to the rock-head brine, which was a highly-saturated solution consisting of one part salt to three parts water. When this supply is pumped up, its place is taken by fresh water, which, flowing over the rock-beds, takes up its quota of salt on its way to the pumping shafts, and is raised to the surface in the form of brine.