LOCAL SURFACE AND UNDERGROUND SPRINGS. 171 



To enable man to get the full benefit from springs re- 

 source is very often had to sinking and boring, as thereby 

 the springs are opened out and expanded so as to meet the 

 wants of the adjacent masses of civilization, and the cost 

 of going further afield for river and surface spring supplies 

 may be obviated. There may be also the further benefit of 

 obtaining water free from sewage contamination and patho- 

 logical organisms, for which the ever-watchful analytical 

 chemists are constantly on the look-out. 



These wells and borings through the different strata 

 are productive of a good deal of useful information, and 

 it is then that we find what a network of underground 

 movement in water and hidden energy is going on of which 

 we should otherwise be perfectly ignorant. For instance, 

 in connection with the huge spring met with in the sink- 

 ing of the Sud brook shaft for the Severn Tunnel, we have 

 an instance of an immense underground river or body of 

 water being suddenly released by being intersected in its 

 course most probably to the Severn. Having had occasion 

 to examine this spring and the adjacent watershed, in con- 

 junction with other engineers, there is no doubt in my 

 mind that this water had its gathering ground far away to 

 the north-west (in the Old Red Sandstone and Mountain 

 Limestone) in the Wentwood Forest and drawing through 

 swallet-holes in the Cas-Troggy Brook (which I have my- 

 self observed), and which formed one source of the 

 numerous feeders to the underground fissures contributing 

 to the huge volume of water intersected. Again, at Ched- 

 dar, on the south-west slope of the Mendips, in the Cheddar 

 Valley we have another instance of a natural outlet of a 

 swallet fed in underground channels situate in the Car- 

 boniferous Limestone having its contributing area extend- 

 ing over a considerable watershed, most probably in an east 



