22 



no streams the natural surface drainage is interfered with 

 and small lakes form, as at Billinge Green and Winnington, 

 near Northwich, and what is called the Ocean, near Winsford. 

 Again, where the marls are thick and tenacious, they 

 remain suspended for a long time, whilst the water is 

 surely and rapidly eating away the underlying rock 

 salt. At last the cavity becomes too large for the marls 

 to bear the overlying earths up, and they fall, taking 

 in a large area of ground, and leaving large holes, 

 like the Marton Hole, that fell in in 1871 (of which I 

 gave an explanation in "Nature" in Feb., 1872), and 

 another in the same district on Bark House Farm, in Sep., 

 1879.* ]n the Northwich salt district some portions are 

 literally honeycombed with old rock salt mines; when the 

 fresh water in its course to the pumping centres passes over 

 the layer of rock salt forming the roof of the mine, in course 

 of time it eats the whole away, and the upper earths fall 

 into the old mine, leaving an enormous crater-like pit, as 

 may be seen in Wincham, near Piatt's Hill old mine, and 

 several other places in the immediate neighbourhood. 

 When the brine stream in its course comes to the shaft 

 of an old mine it runs down it and fills the mine. All 

 over the Dunkirk district of Northwich, and in Marston, 

 there are pits of this description full of brine. When these 

 enormous reservoirs, covering at least 80 acres in the above 

 districts, are nearly pumped out, it frequently happens that 

 the streams above find a way down into them and cause 

 great destruction, as is the case in Marston, where a lake of 

 at least twelve acres has been formed in this way during 



* A large number of small holes 9 or 10ft. in diameter, andf rem a few- 

 feet to 10 or 12 in depth, have fallen in near Northwich, taking in 

 roads, river banks, and parts of fields. 



