Vol. 55.] ANNITEESAEY ADDEESS OF THE PEESIDENT. Ixix 



I COME now to the last and most troublesome part of my duty, 

 for it is by no means easy, to me at least, to find a subject worthy 

 of your consideration on this occasion, and to treat it in a befitting 

 manner. 



In the few remarks that I have to make, I desire to draw your 

 attention to some matters in which our science has a practical 

 application. Its bearing on questions of mining has been brought 

 before you at various times ; but it is in connexion with the health, 

 rather than with the wealth, of the nation that I wish to speak. 



The great subject of Water-supply has been discussed by some of 

 my predecessors, but only, I believe, in regard to London, not 

 generally. Now, the water-supply of London is a subject pro- 

 vocative of endless controversy : it has not been settled by a 

 series of Eoyal Commissions and other kindred enquiries ; indeed 

 it seems still as far from being settled as ever, and to be the 

 unsolved riddle of the century. I should not like to enter upon 

 its consideration now, in an address that is not discussed, though 

 personally I should j)refer a discussion to an address. 



I am inclined to think that comparatively few geologists realize 

 the importance of geological considerations in matters of Water- 

 supply. Whether water is got simply by taking it as it comes 

 from springs, or by impounding it in reservoirs on its way down 

 streams, or by means of wells and borings (the three methods into 

 which schemes for water-supply may be roughly grouped), however it 

 is got, in fact, a knowledge of the character of the gathering-ground 

 is essential, and this knowledge depends largely on geology. 



In the selection of sites for reservoirs more particular points 

 have to be considered, especially where high dams are to be 

 constructed. In such work it is weU, as far as possible, to avoid 

 places where there is any great disturbance, whether by faulting or 

 otherwise. 



Masses of Drift, too, are sometimes troublesome, and it may be 

 needful to study the composition of these and their relation to the 

 rocks beneath : irregular mixtures of permeable and impermeable 

 yielding material are likely to cause trouble, and the uneven 

 way in which Drift so often occurs leads to uncertainty as to 

 its thickness. On the whole, therefore, those parts of a valley 

 with much Drift are to be avoided, although sometimes a bank or 

 sheet of solid Boulder Clay may be useful. Prof. Boyd Dawkins 

 has lately drawn attention to this matter, in a lecture delivered to 

 the Institution of Civil Engineers,^ noticing a case, at the Ogden 

 ^ Proc. Inst. Civ. Eng. vol. cxxxiv (1898) p. 270. 



