WATER SUPPLY AND PUBLIC HEALTH. 
41 
The hardness remaining after softening is due to the pre- 
sence of sulphate of lime or sulphate of magnesia; this is 
termed 44 permanent hardness.” 
The plans which have been suggested for supplying London 
with water from distant sources, as from Wales and the Lake 
District, are those most frequently spoken of when dissatisfac- 
tion is expressed with regard to the present supply. This is 
not to be wondered at, for the schemes are bold and complete, 
the water promised is pure and abundant. Compared with 
these, the proposals for collecting spring and well water in 
various parts of the Thames basin, and bringing it by different 
routes to London, are 44 patchy” and tame; and yet perhaps 
in these characters lie their chief recommendation. Is it 
wise to trust for the supply of the metropolis to a single source, 
so far distant? Moreover, these distant sources may some 
day be wanted for the towns in the northern and midland 
districts. 
There seems no necessity for going so far away, as plenty of 
good water can be obtained within the Thames basin itself. 
Indeed, no large city is better situated for supplying itself from 
within its own drainage area ; although some — Paris, for in- 
stance — are more fortunate as regards deep wells. The average 
daily supply from the metropolitan companies during 1874 was 
116,500,000 gallons, or 34*8 gallons per head; the maximum 
daily supply was in September, when it averaged 127,600,000 
gallons, or 37*5 gallons per head. It is calculated that about 
one-third of the supply is wasted ; one-third goes for trade 
purposes, flushing sewers, street watering, and fires ; only one- 
third is used for purely domestic purposes. 
The Commissioners on Water Supply estimated that it would 
be desirable to calculate on a future population of 5 millions, 
with a maximum summer consumption of 200 million gallons, 
or 40 gallons per head. The present excessive waste can be 
largely checked by the use of better fittings and more strict 
control; by such means the consumption in Liverpool has 
been reduced by Mr. Deacon from 28*89 to 16*47 per head, 
under constant service. But, to be on the safe side, we will 
take the figures as they stand. One reason for doing so is the 
'possibility that the Thames valley may some day become a 
busy centre of mining industry. Geologists have long surmised 
that under the south-east of England there may lie fields of 
valuable coal measures, at a workable depth.* The Sub- 
* Professor Prestwich has fully discussed this question in a former 
number of this Review (vol. xi. p. 22 5 • 1872). The Metropolitan Board 
of Works are now putting down a boring at Crossness, which they intend to 
carry through the Gault. This is in search of water, but its results will 
