10 



upon the rock salt ; this soon cuts a small channel in the 

 salt, which widens and deepens to such an extent that large 

 blocks of salt easily become detached. Unfortunately for 

 the miners by this method, the water running too quickly 

 to become saturated passes away to the sole of the mine 

 and there completes its saturation, very frequently under- 

 mining the pillars left to support the roof of the mine and 

 causing great destruction. 



In the Cheshire salt district enormous damage has been 

 caused by water passing from the upper strata over the sur- 

 face of the first salt bed and down the face of the salt ex- 

 posed in the shaft to the mine below. Nearly all the oldest 

 mines have been destroyed in this way. These mines were 

 in the upper bed of rock salt, which was discovered in 1670 

 but not worked for a number of years after this. In 1781 

 the lower bed of rock salt was discovered, and a year or 

 two after this mines were worked in the lower bed and 

 those in the upper bed gradually abandoned. The history 

 of the neighbourhood of Northwich from about 1750 to the 

 present time is a constant repetition of the falling in of old 

 mines. In almost every case known this was caused by 

 water. The sinking takes place near the shaft, which is 

 naturally the weakest place, and at first resembles a well 

 but continually enlarges in size till it is 50, 60, or even 100 

 feet in diameter. After this the sides crumble down till the 

 hole chokes at the bottom and a funnel or crater remains 

 which in time fills with water and becomes one of the 

 numerous pits in the neighbourhood of Northwich known 

 as rock pit holes. I have recently had several opportunities 

 of seeing the process in action. Water trickling down a 

 shaft in Wincham — still standing — has channeled the rock 

 salt so deeply that in parts it has the appearance of the 

 columns of a church or cathedral. The cavities or flutings 

 are in many places several feet deep, and the shaft, instead 

 of being 4 to 5 feet in diameter, is from 12 to 15 feet. In 



