Vol. 55.] ANNIVERSARY ADDRESS OF THE PRESIDENT. IxXl 



been observed, especially in the later work of the Geological 

 Survey. 



Another matter that may give trouble in a reservoir, and 

 has to be guarded against, is the occurrence of permeable beds 

 through which the water may find a way to lower ground, under 

 favourable circumstances. An example of this may be given from 

 another set of reservoirs of a like kind to that already noticed, along 

 the valley of the Loxley, for the supply of Sheffield, That portion of 

 the valley in which the reservoirs are placed is cut out of the upper 

 part of the Millstone Grit Series, which consists of alternations of grits 

 and shales. From the slight easterly dip of the beds, down the valley 

 and at a higher angle than the bottom-slope, the Middle Coal 

 Measures are carried down to the bottom by the eastern end of the 

 Damflask Reservoir, and in part the sides and bottom of this 

 reservoir consist of a porous grit, down which water passed to below 

 the dam. To get over this difficulty, a long trench had to be made 

 along the southern side and filled with watertight materials. 



Coming to the consideration of the supply of water by means of 

 wells, many important geological problems are brought before us, 

 and some of these would otherwise escape notice. We are also 

 reminded of the frequent dependence of one science upon another, 

 and in this case we are specially concerned with chemistry. 



Underground water is indeed a very complicated and difficult 

 subject, making strong calls on our reasoning powers. In the case 

 of springs and of streams we are dealing with facts, things that 

 anyone can see ; but in the case of underground water it is a very 

 different matter: we have to make inferences, and though our 

 inferences may be warranted by all that is known on the subject, 

 yet it is seldom that we can speak with certainty. There is, there- 

 fore, a certain charm in questions as to underground water that 

 is wanting in the more prosaic subject of surface-waters. 



Besides the element of chance, generally so delightful to frail 

 humanity, the perhaps still more delightful element of superstition 

 (for want of a better name) also comes in, and of late the divining- 

 rod has been a good deal in evidence. I am not going to enter 

 into so awful a question as to whether a forked twig can or cannot 

 point out where water may be got : the literature of that subject is 

 large enough already ; but I should like to call attention to the 

 curious fact that among the believers there are many educated 

 persons, clergymen, peers, squires, etc. In a recent essay on water- 



VOL. LV. / 



