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we may expect that the period has arrived at which further 
increase of population will he absolutely impossible ; but I 
trust we are as yet far from that position. 
The increase of towns, and the sanitary improvements 
which have taken place, particularly those which have been 
carried out with reference to sewerage, and various manu- 
facturing operations, have so polluted the rivers that many of 
them are no longer fit for the domestic wants of the inha- 
bitants. Still, there is upon the hills and in the bowels of the 
earth sufficient pure water to be collected for all these wants. 
It may be of some interest to take a general survey of the 
means which may be adopted for obtaining such supplies. 
Water may be collected in reservoirs or tanks as it used to 
be and still is in Ceylon and India and elsewhere ; it may be 
obtained from rivers which are yet unpolluted, or from natural 
lakes ; it may be collected, as it is in some instances, from 
springs ; and it may be extracted from some geological forma- 
tions from the bowels of the earth ; but all water, whether 
that in rivers or in lakes, or in springs, or in the earth below 
the surface, depends upon the quantity of rain which falls, 
and it is, therefore, matter of interest to ascertain what it is 
that we have to depend upon. 
The rain varies, as I have said, to a very considerable ex- 
tent. Apart from those mountain regions in which the rain 
may be said to be excessive, that which falls upon the 
western coast of England and in Ireland measures between 
30 and 40 inches in a year, while that which falls on the east 
coast of England will not much exceed 20 inches, being little 
more than half of that which falls in Ireland or upon the western 
coast of England. 
The agricultural produce of the districts varies in great 
measure, in consequence of this different deposition of raiu. 
Ireland and the western coast of England are essentially 
grazing-countries, while, generally speaking, the eastern 
coast of England is devoted to the production of grain. 
The reason why Ireland and the western coast receive more 
rain than the eastern coast is because the prevalent rain- 
bearing winds are from the Atlantic ocean. The mountains 
and the high lands, which are generally colder than the low 
lands, condense the vapour contained in the rain clouds, and 
cause an early precipitation upon the land. As the clouds are 
driven on by the wind, they gradually lose their watery 
character, and the rain which is precipitated is consequently 
constantly decreasing as the clouds pass from west and south- 
west to the east or north-east. 
Thus the rain which falls upon low hills not exceeding 
