exvil 
figures are given in the table before you, also analyses of Hobart and 
other waters for comparison. In dealing with my subject, the consider- 
able outside interest, and I am sorry to have to add ignorance, which 
attach to it must be my excuse for repeating and emphasising many 
points with which you are already familiar, but the knowledge of 
which is not so widespread as it should be. I propose to begin with 
the impurities found in different classes of water, to define the conditions 
which a really good natural water should fulfil, and to point out some 
means which may be employed for the improvement of a bad or sus- 
picious water, in cases where no other supply above suspicion is by 
any means obtainable. 
Foreign Matters found in Waters. 
Chemically speaking, no water found in nature is pure; the impuri- 
ties are very various—gaseous, liquid, and solid, organic, and inorganic 
—some beneficial, some harmless, some deadly in their effects when 
introduced into the human body; but the word ‘“‘impurity ” for our 
present purpose may be taken to mean something objectionable either 
in itself, in its origin, or its excessive quantity. The gaseous consti- 
tuents of natural waters are mainly oxygen, nitrogen, and carbonic 
acid, all present in the air, and beneficial or harmless ; small quantities 
of carburetted hydrogen in marsh waters, and sulphuretted hydrogen 
with its unmistakable smell like rotten eggs in some mineral waters. 
The usual mineral or inorganic constituents are lime, magnesia, potash, 
soda, and ammonia, with sometimes iron, manganese, or alumina, 
combined with chlorine, sulphuric, carbonic, and nitric acids, in some 
cases also nitrous, silicic, and phosphoric acids; forming chlorides, 
sulphates, carbonates, nitrates, nitrites, silicates, and phosphates. 
Nct one of these substances is, in itself, injurious, if in small quantity; 
but the amounts of ammonia, nitrous and nitric acids, and chlorine 
are used with other results of analysis in forming an opinion as to the 
purity or otherwise of the water under examination, while anything more 
than the most minute trace of phosphoric acid is considered a certain 
indication of sewage contamination. 
The more or less poisonous metals, arsenic, lead, copper, and zinc are 
sometimes found, derived either from minerals in the rocks, or from 
pipes and tanks. The use of zinc-coated or galvanised tanks has been 
discontinued in the French navy on account of the action of water in 
dissolving zinc. The remaining constituents found in water are vavious 
kinds of organic matter, that is, matter of animal or vegetable origin, 
both dissolved andin suspension ; the suspended matter is in part dead 
and decaying, the remainder consisting of innumerable minute living 
organisms of many kinds, sometimes including water-fleas and worms, 
and the ova of parasitic worms of men and animals, and almost always 
some forms of fungi, alge, etc., or infusoria, the immense variety of the 
last named class being shown in Mr. Saville-Kent’s wonderful manual 
lying before you. Amongst the fungi are classed the schizomycetes, 
minute, mostly colourless cells or threads, globular, in short rods, or 
straight or spiral filaments embracing the various species of bacterium, 
bacillus, spirillum, micrococcus, vibrio, etc., they include the smallest 
organised bodies known, and asa class may be said to measure from 
1-150th to 1-15,000th of an inch, they multiply in two ways, either by 
the splitting up of one into two or more individuals, or by the coal- 
escence of two organisms into one, followed by the production of 
spores which develop into the parent form. Most of these species must 
be considered harmless, if we take into consideration their world-wide 
distribution, both in air and water, and the fact that they, as well 
as the other impurities mentioned, with the exception of the parasitic 
ova, associated as they too frequently are with excrementitious 
matters, are daily swallowed by millions of people without apparent 
