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water down artificially, for, owing to the numerous mines 

 and subsidences of land, the ground is rifted and fractured, 

 and no sooner has the brine pumper exhausted one of the 

 old mines, or even only partially exhausted it, than the 

 water from the overlying brooks or pits finds its way down 

 and fills up the cavity once more. These downrushes of 

 fresh water are doing a vast amount of damage, and in the 

 course of a few years a large portion of the districts known 

 as Dunkirk and Marston, in the proximity of these reservoirs, 

 will be completely destroyed and under water. » 



I have only attempted to generalise the vast body of facts 

 bearing upon the subject of this paper, but I think it must 

 be clear that fresh water is always destructive to rock salt 

 whenever it comes in contact with it ; but that, except the 

 beds of salt lie above the general level of the country and 

 its drainage system, and are exposed either as mountains, or 

 as partial outcrops in valleys, no destruction perceptible 

 occurs, and in the cases of rock salt thus occurring the waste 

 is comparatively small and harmless. On the other hand, 

 whenever man, either by utilising the natural springs, or 

 sinking fresh shafts to the underlying brine and causing 

 a more rapid circulation of the underground waters that 

 reach the salt beds, or where there is no natural brine — 

 pouring down water upon the salt bed and pumping it up 

 as saturated brine — interferes with the operations of nature, 

 waste is more rapid and surface damage increases in the 

 direct ratio in which man accelerates the ordinary natural 

 operations. Where man only utilises the amount of brine 

 running to waste in springs his operations produce no 

 visible surface effects ; it is only when he causes a purely 

 artificial state of affairs that mischief follows. Having in 

 a former paper traced the growth of the surface damage side 



