172 FKAGMENTS OF SCIENCE. 



Chalk-water. Clark's Softening Process. 



But is it not possible to match the water of the Lake 

 of Geneva here in England ? Undoubtedly it is. We 

 have in England a kind of rock which constitutes at once 

 an exceedingly clean recipient and a natural filter, and 

 from which we can obtain water extremely free from 

 mechanical impurities. I refer to the chalk formation, 

 in which large quantities of water are held in store. 

 Our chalk hills are in most cases covered with thin 

 layers of soil, and with very scanty vegetation. Neither 

 opposes much obstacle to the entry of the rain into the 

 chalk, where any organic impurity which the water may 

 carry in is soon oxidised and rendered harmless. Those 

 who have scampered like myself over the downs of 

 Hants and Wilts will remember the scarcity of water in 

 these regions. In fact, the rainfall, instead of washing 

 the surface and collecting in streams, sinks into the 

 fissured chalk and percolates through it. When this 

 formation is suitably tapped, we obtain water of ex- 

 ceeding briskness and purity. A large glass globe, 

 filled with the water of a well near Tring, shows itself 

 to be wonderfully free from mechanical impurity. 

 Indeed, it stands to reason that water wholly withdrawn 

 from surface contamination, and percolating through so 

 clean a substance, should be pure. It has been a 

 subject much debated, whether the supply of excellent 

 water which the chalk holds in store could not be ren- 

 dered available for London. Many of the most eminent 

 engineers and chemists have ardently recommended this 

 source, and have sought to show, not only that its 

 purity is unrivalled, but that its quantity is practically 

 inexhaustible. Data sufficient to test this are now, I 

 believe, in existence ; the number of wells sunk in the 



