and Water used for General Puiyoses. 
147 
in which primitive rocks prevail, are superior to chalk-springes ; 
but, unfortunately, very soft waters are frequently coloured by 
organic matter, and, as a rule, act upon leaden pipes more ener- 
getically, and are more liable to become contaminated with 
soluble compounds of lead, than hard waters ; and this circum- 
stance presents certain disadvantages to the use of very soft 
waters, such as those from the Cumberland or Scottish lakes. 
In the examination of water, particular attention should be 
paid to ascertain the quantity of organic matter which a given 
sample may contain, and also to trace, if possible, the origin 
of the organic impurities, and to determine whether they pro- 
ceed from decomposing animal-refuse matters, or from harmless 
vegetable matter, which is frequently found in lake-waters in 
peaty localities. Inattention to the discrimination of the kind 
of the organic matter in a water may lead the analyst to form 
an erroneous opinion of its true character. 
Wholesome and perfectly unobjectionable waters are always 
bright and free from colour. If a water has a yellowish colour, 
and at the same time a more or less nauseous taste or smell, no 
chemical analysis is required to prove its unfitness as a beverage ; 
for such water is certain to contain decomposing organic matter 
of animal origin, which cannot fail to be a source of serious 
danger to the health of those who drink it habitually. Light 
floating particles of suspended organic matter also frequently 
afford indications of the unwholesome character of water. 
It is well, therefore, to submit water to a preliminary examina- 
tion, upon the result of which it will depend whether it is desirable 
to incur the expense of a thorough chemical ansjysis. 
In the first place, I would ascertain whether the water is 
colourless, or more or less tinged yellow. This may be done 
by filling a glass tube, 2 ft. long and about IJ in. wide, with 
the water, placing the tube upon a sheet of white paper, and 
comparing the colour of the water as seen when looked through 
the whole length of the tube with the colour of pure distilled 
water contained in a tube of the same length and diameter. Or 
the colour may be noted by filling a white Bohemian-glass flask, 
I holding about a quart, and placing it on a sheet of white paper, 
and placing by its side a flask of the same size, filled with pure 
distilled water. The best drinking-water appears as colourless 
I as pure distilled water. Most river-waters show a greenish tint ; 
and peaty waters and waters contaminated with yard-drainage 
or sewage, often appear more or less yellow coloured. By the 
same experiment the presence of any small floating particles 
may be readily detected in the water, when the flask is held in 
Iront of a dark-coloured wall, a strong light falling on the flask 
from one side or from above. Should the water contain much 
L 2 
