128 On the Composition and Properties of Dri)iking-Watcr, 
and contributing to the comforts of domestic life. It has been 
surmised that waters which have their origin in crowded cities, 
or in their immediate neighbourhood, must contain ingredients 
incompatible with their use as a beverage or for general domestic 
purposes. The sudden outbreak of cholera, and the prevalence 
of typhoid fever and other infectious diseases, in certain localities, 
have long been associated in the popular mind with bad water 
and impure air ; and there can be no doubt of the great influ- 
•ence which the purity of air and water exerts on general health. 
In manv cases the sudden outbreak of cholera, scarlet and 
typhoid fever, small-pox, and similar diseases, in particular 
towns or districts has been clearly traced to the pernicious con- 
tamination with sewage of the water used by the inhabitants, 
or to the infiltration of surface-drainage into the wells which 
supplied the drinking-water. Most towns in England at present 
are supplied with wholesome water, which is often brought to the 
■door of the consumer from considerable distances ; and the town 
population in most places is no longer dependent for its water 
upon local wells and pumps, many of which have been closed alto- 
gether by the sanitary authorities. The examination of a largo 
number of samples of water from towns and the country leads 
me to the conclusion that towns, as a rule, are supplied with 
purer drinking-water, and water better suited for general house- 
hold purposes, than counti'y districts, isolated farmhouses, and 
<;ountry residences. 
The suppl}' of water in rural districts is often not only deficient 
in quantity, but frequently largely impregnated with sewage 
and yard and house drainage, being thus rendered unwholesome, 
and quite unfit for drinking purposes. There are many villages 
with no other source of supply than shallow wells ; and even the 
•country residences of the nobility and landed proprietors I find 
frequently are supplied with unwholesome water, or water much 
less pure than that in use in most towns. 
The purity and suitability for general household purposes of 
spring, river, and well waters, in the first place, are influenced 
by the chemical composition of the rocks of the locality in 
■which they originate ; and in the second place the properties 
of natural waters are more or less affected by local sources of 
contamination, such as the proximity of the well to a cesspool, 
a liouse or yard drain, a stable-yard or a dung-pit. 
If a water emits a strongly disagreeable smell, or if it is more 
or less coloured yellow, or if it is turbid, or if it shows floccu- 
lent, floating particles of organic matter or living organisms, 
no chemical examination is requisite to prove its unwholesome 
character and unfitness for drinking purposes. It, however, 
frequently ha])pens that fairly bright and barely coloured water, 
