and Water used for General Purpose!'. 
129 
emitting no smell whatever, nevertheless may be impregnated 
with an amount of organic impurities and certain saline in- 
gredients which will render it unfit for drinking and cooking 
purposes. By a careful chemical and physical examination it 
may be decided without much difficulty, in many cases, whether 
or not water is fit for drinking, and which of a number of 
samples is best adapted for general domestic purposes. In other 
instances the analytical indications are less decisive, and the 
water will have to be pronounced of a suspicious or doubtful, 
or, at all events, not perfectly wholesome character. 
I purpose in the following pages to pass in review the various 
kinds of natural waters, pointing out their composition, pro- 
perties, and adaptation for household purposes ; next to direct 
special attention to the sources of contamination which render 
water more or less unwholesome or unfit for domestic use ; and 
lastly, as far as practicable, to point out any available means for 
purifying water. 
The principal varieties of natural waters are rain-water, 
spring-, river-, well-, and sea-water. The latter may be dis- 
missed at once, the purport of this paper being to treat of waters 
which are used for domestic purposes. The remaining varieties 
may be conveniently placed in two groups, and described as 
soft and hard waters. There is, however, no distinct line of 
demarcation separating the two groups, for the difference be- 
tween hard and soft waters is one of degree and not of kind. 
Speaking generally, a water is called soft if it contains per im- 
perial gallon not more than 12 to 15 grains of fixed constituents, 
the greater part of which consists ot carbonate and sulphate 
of lime and magnesia. If there are more than 8 to 10 grains of 
lime and magnesia compounds in the total fixed residue, and 
the amount does not exceed 16 grains, the water is said to be 
moderately hard ; and if the earthy matters exceed 16 grains in 
the gallon it is considered decidedly hard. 
Soft Waters. 
Rain-water. — In nature, water is never found perfectly pure. 
The impurity of the water is frequently visible to the eye. Fine 
suspended red clay often imparts a reddish colour to rivers 
flowing through rocks of red marl, which contain much oxide 
of iron in their composition ; occasionally it appears milky, 
from fine particles of white clay, which settle with difficulty 
or only imperfectly after long subsidence. In other instances 
river-water is contaminated with town-sewage and then ap- 
pears muddy and more or less dark-coloured. It is generally 
brown where it issues from boggy lakes or passes across a 
VOL. XI. — S. S. K 
