18G7.] On the future Water-supply of London. 51 



at different times, according to slight changes of climate and slow 

 movements of the surface, and it is in accordance with all we know 

 of the laws that have determined the distribution of animals, that so 

 striking a modification of the physical geography of a country as the 

 formation of thousands of lakes should lead to many changes and 

 restrictions of the ranges of all animals, and especially of the fishes. 

 The lakes may have proved more congenial to some which had 

 hitherto been confined to one or two streams only, and may have 

 preserved others from extinction which were just dying out. But 

 on the iceberg theory the difficulty is immensely greater ; for all 

 the country north of the lakes (and much also south of them) as 

 well as westward, almost to the bases of the rocky mountains, is so 

 level that it must have been all under the ocean together ; and it 

 becomes difficult to understand where the great variety of fishes 

 now inhabiting the streams and lakes of these regions can have 

 come from, or how in so comparatively short a time they can 

 have become modified into distinct local species. I leave this inter- 

 esting ice-problem to those among my readers who take an interest 

 in the great case of " Glacier v. Iceberg," now being argued in the 

 High Court of Physical Science. 



V. THE FUTUKE WATEK-SUPPLY OF LONDON. 



By Edwaed Hull, B.A., F.G.S., of the Geological Survey of 



Great Britain. 



The next Session of Parliament will probably be occupied with the 

 consideration of two rival schemes for the supply of the Metropolis 

 with water from distant sources, planned by engineers of eminence 

 on gigantic proportions. That some distant source of supply is 

 needed to replace the present arrangement, has been for some 

 years foreseen by those who have taken an interest in the matter. 

 Not only is the water from the Thames, the Lea, and other sources 

 from which the Water Companies draw their supplies, destined 

 shortly to become insufficient for the requirements of the inhabit- 

 ants, but it is far from pure, containing in sensible quantities not 

 only the salts of hme and magnesia which render it " hard," but 

 organic matter derived from the villages and towns situated along the 

 banks of these streams. Now of all the disadvantages which can 

 effect a large city none is more intolerable than the want of pure 

 water. It is a prime necessity of health and comfort, which every 

 day's experience renders more obvious ; nor can we doubt that the 



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