MANUFACTURE OF SALT IN CHESHIRE. 23 



this manner, by water, no provision can be made for the 

 support of the roof of overlying earths, as is done by pillars 

 in the ordinary mine. The brine streams, or brine " runs," 

 as they are called, resemble brooks and rivulets into which 

 the waters run from all sides and drain the surface. The 

 course of these underground streams is marked by a cor- 

 responding depression on the surface of the ground. The 

 land sinks more rapidly directly over the brine-runs than 

 elsewhere, though there is a gradual lowering of the surface 

 of the rock salt generally, even out of the line of the runs — 

 exactly as there is a gradual lowering of the surface of the 

 land by the solid earths and sands carried away by the 

 water draining off it. The salt, however, being so much 

 more soluble than earths, the process is much more rapid. 

 In some cases the overlying earths follow the gradually wast- 

 ingrock salt continuously, and the subsidence on the surface 

 is regular and continuous ; in other cases, where there hap- 

 pens to be a tenacious " flag M or other stiff and solid earths, 

 the superincumbent mass remains suspended over the brine- 

 run for a long time. As soon, however, as the weight of 

 the suspended mass overcomes the tenacity of the marl or 

 flag, a sudden sinking of the whole overlying earths takes 

 place, and a large hole reaching up to the surface is formed, 

 which in time becomes filled with water. 



In recent years a number of these holes have been formed 

 in the neighbourhood of Winsford and Northwich. In the 

 neighbourhood of Northwich they have been formed chiefly 

 over old mines. Instead of the hollow being made naturally, 

 as near Winsford, by the ordinary brine-run, it has been 

 made artificially by the miner. In both cases, however, 

 the sudden sinkings are directly caused by the pumping of 

 the brine. Whenever any sinking, whether gradual or 

 sudden, occurs in the neighbourhood of a brook or river 

 (and the majority occur in such positions) , the water soon 



