164 
influences, and describes the disease as produced by “a poison 
which is generated in the bodies of those who suffer from the 
disease, but which is capable of “ving, and probably of muz/tiplying, 
in water containing decomposing organic matter. 
Briefly, I may say that this disease (cholera) is now under- 
stood to be generally conveyed by water containing its germs ; 
and although no means are yet known by which these germs—or 
any other disease germs—may be detected, except by their actual 
influence upon persons exposed to them, yet chemistry enables us 
to say when water contains substances which usually accompany 
them, and which assist in their re-production. This branch of 
chemistry—the analytical examination of potable water—is one 
which has very properly received, and is still receiving, a great 
amount of consideration. 
The questions to be asked are— 
(1) WHaT IS WHOLESOME WATER? and 
(2) How MAY WE KNOW WHEN WATER IS WHOLESOME ? 
Pure water, such as we prepare by distilling that which we 
have in abundance around us, is composed of two gases—oxygen 
and hydrogen, chemically combined ; but when we examine such 
water as we have about us in wells or streams, we find it to contain 
other substances in greater or less proportions; and it is to the 
quantity and character—more especially the character—of these 
additional substances that the purity or otherwise, the suitability 
or otherwise, of the water for domestic use is due. Thus, by 
analysing a sample of water, and determining the amount and 
character of the additional substances, we obtain a knowledge 
which may enable us to say whether it is suitable for drinking 
purposes or not. 
The purest form of natural water is that which falls in the 
country either as snow, hail, or rain; but as soon as it reaches 
the earth, it begins to dissolve various substances from it, which 
too often, when drunk, are injurious. The artificial constructions 
of man, so various and so numerous, first render the soil impure, 
and then the soil contaminates the water he has to drink. The 
water of deep wells is often purified from the surface pollutions by 
the deep strata through which it has passed; and in this district 
this is often the case. I have received samples of exceptional 
