^^^^' 55-] ANNIVERSARY ADDRESS OF THE PRESIDENT, IxXV 



other subjects which not unfreqiiently conflict somewhat with the 

 former. Sites have, unfortunately, to be found for sewage-farms 

 and for burial-grounds. For these, soils that have a fair amount of 

 porosity are advantageous, and thus there is often a tendency to place 

 them on water-bearing formations. 



In the matter of sewage-farms, it would be of little use to establish 

 one on a stiff clay, except after a surface has been artificially pre- 

 pared, a costly operation. Where, however, our great spreads of 

 clay have cappings of sand, gravel or loam, good sites may be found, 

 as at the well-known sewage-farm for Croydon, which is on the 

 gravel of the Wandle Valley at Beddington. It is clear, therefore, 

 that a geological map without Drift is comparatively useless in 

 seeking for sites for the disposal of sewage. I well remember 

 giving evidence, officially, as a member of the Geological Survey, 

 before a Eoyal Commission that was investigating the disposal 

 of the sewage of a not unimportant place, and that had duly 

 provided itself with the Geological Survey map. It was found, 

 however, that the particular maps supplied were of the usual kind, 

 without Drift. On producing the proper article I was much pleased 

 with the expression of the Chairman, the late Lord Bramwell, as to 

 the comparative value of the two maps, albeit that it was made in 

 language by no means complimentary to the Driftless map. As a 

 matter of fact, the Drift map made a certain scheme worthy of 

 being considered, which without it would have been at once passed 

 by as absurd. 



With regard to sewage-farms, etc., it is of course important that 

 sites should not be used whence damage may result to water- 

 supplies, and this is often a difficult matter to determine. It 

 seems, however, as if processes were coming to the front which 

 may enable us to make sewage-effluents harmless ; but even should 

 that be the case, we ought still to guard our water-supplies from 

 risk, and in doing this geology gives important help. 



As to burial-grounds, one may notice the requirements, or rather 

 suggestions, of the Local Government Board, originally drawn up by 

 one of our Fellows (Dr. F. Parsons), as follows : — ' The soil of a 

 cemetery should be of an open porous nature, with numerous close 

 interstices, through which air and moisture may pass in a finely 

 divided state freely in every direction. In such a soil decay 

 proceeds rapidly, and the products of decomposition are absorbed 



