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per gallon to 19.04; while the New River water has
averaged 18.31 grains per gallon, the River Lea
18.62 grains, and the water from the chalk wells
27.31 grains. The hardness of the general supply
has been about 14 degrees, and this has been reduced
by boiling to rather less than 4 degrees; but the
chalk water has had an average hardness of 20 degrees
before boiling, and 5.2 degrees after. As to the
proportion of organic matter in the water, it has
been very small, for the quantity of oxygen required
to act on every description of oxydisable matter has
ranged from only 0.011 of a grain per gallon to
0.085; and the proportions of ammonia, and of
organic nitrogen have never reached beyond the one
four thousandth part of a grain per gallon of water.
As public attention has been again directed to the
question of supplying London with soft water, I have
taken some pains to ascertain the comparative salubrity
of the places in England and Scotland which
are supplied with hard and soft water; and in addition
to the 19 large towns, whose death-rates are constantly
reported by the Registrar General, I have
obtained from his office the average birth-rates and
death-rates of many other cities and towns of
England during the five years (1861—1866), and
the general results of these inquiries are expressed
in the following tables :—