AS SOURCES OF WATER-SUPPLY FOR TOWNS. 267 



vicissitudes of long droughts. Wlien these occur of more 

 than ordinary length, the brooks dry up and the water 

 fails ; but in the underground reservoirs of the strata, the 

 circulation of the water is so slow throughout the mass 

 that the supply is economized, and is capable of holding 

 out for lengthened periods. Yet both the towns above- 

 named have preferred placing reliance on these variable 

 sources in preference to those of a more constant cha- 

 racter. 



The advantages afforded by the New Red Sandstone 

 have often been thrown away by an improper selection of 

 positions in sinking wells. Through ignorance of the geo- 

 logical structure of the district from which it is proposed 

 to draw a supply, large sums of money have been uselessly 

 expended. The case of Wolverhampton may be instanced. 

 This town, naturally well placed for drawing a supply of 

 water from the New Red Sandstone, has been obliged to 

 have recourse to a river many miles off to minister to its 

 necessities — a result due to the selection, in the first in- 

 stance, of an improper site for the well (see fig. 2). The 

 case of Rugby was one of another kind. For here there 

 was no New Red Sandstone from which to draw, and the 

 discovery of salt water in the strata of the Red Marl 

 might have been anticipated, as it is the same formation 

 which produces the brine- springs of Cheshire and Wor- 

 cestershire. (See diagram, fig. 1, p. 259). 



How to find water in the natural reservoirs of the strata 

 is every day becoming more and more a geological ques- 

 tion. It cannot be too strongly urged that, in order to 

 solve this problem, a knowledge of the composition, pro- 

 perties, and structure of the rocks is indispensable — -just as 

 much so, in fact, as. in the question of finding coal. The 

 following suggestions may therefore be of service as rules 

 of general application : — 



It may be almost always expected that the water will 



