188 THE MICROSCOPICAL NEWS. 
villages is poured into the river. The sewage of Chester, and the 
refuse of numerous works and factories, also run into it below the 
weir at Chester. So it is obvious that water obtained from such a 
source can only be pronounced safe for drinking purposes if all the 
sewage and other organic impurities be eliminated by most careful 
and perfect filtration. In spite, however, of the amount of pollu- 
tion thus indicated it is very often possible to see the river bed quite 
clearly in parts where the water is only a few feet deep. Although 
occasionally so clear, there is always a most strongly-marked dif- 
ference in the transparency of the water before and after filtration 
through the filter-beds of the works. A column of the filtered water, 
one yard long, is clear enough to read threugh, whilst such a column 
of unfiltered water entirely obscures the view. As might be-expected 
a microscopical examination of the sediment obtained from the top 
of the filter-beds, or of the river water at the source of supply, 
reveals contamination of the water with what has been termed 
“household refuse,” in addition to the ordinary aquatic animal and 
vegetable organisms. All of these constituents are still present, 
but in vastly inferior quantities in the water after filtration. The 
utmost pains are taken by the water company to secure perfect 
filtration, and their efforts are successful in a very high degree, so 
much so, indeed, that the water now supplied to Chester is pro- 
bably as bright, clear, tasteless, and good as any in the kingdom. 
Still the incontrovertible fact remains that some particles of appreci- 
able size and recognisable form pass through the filter-beds and 
find their way into circulation. A simple microscopical examin- 
tion therefore plainly suggests that no watercourse from which water 
is obtained for drinking purposes should ever be permitted to re- 
ceive sewage, as if once in, no system of filtration seems competent 
to remove it. As with milk so with water,—the obvious teaching of 
the whole matter is, rigorously to guard against the introduction of 
any excrementitious impurities into either of them. It may cost 
money to bring about the needful reforms in both cases. But men’s 
lives are at stake, and they surely are not to be estimated at a 
money value. Great dependence is sometimes—in fact by most 
people—placed on the purifying power of domestic filters. Many 
of them are very good, some are very bad; but a very simple 
experiment will prove to anyone that the best of them is not capable 
of removing the more minute germs of certain organisms. Draw 
say a quart of water from the filter, seal it up in a white glass 
bottle the cleanliness of which has been properly assured, place the 
bottle in direct sunlight for a week or fortnight, and the germs 
which have defied filtration will multiply so rapidly as to become 
visible even to the naked eye. If, therefore, the germs of Algz 
&c., pass through the filter, so also with others, perhaps more 
dangerous, A filter should only be looked upon as a sieve. Many 
