ON WATEE-FILTEES. 
By EDWARD DIVERS, M.D., F.C.S., 
Lecturer on Natural Philosophy, Charing Cross Hospital. 
<4 T)EEVENTION is better than cure ” is a ffiaxim no less true of 
JL foul water than it is of disease. But we cannot always act 
upon it in the one case any more than in the other. Eiches cer- 
tainly may do much in preserving health, but then there are the 
many circumstances affecting it which are beyond human control 
and the force of riches. To a much greater extent, however, can 
money ensure the obtaining and preservation of pure drinking- 
water. Nevertheless, besides the comparatively narrow cases of the 
voyager and the explorer, there is one case which directly con- 
cerns millions where money practically fails to procure a pure 
supply of water; and that is the case, which applies to the 
dweller in London and so many other large towns, of living in a 
rich community the corporate authorities of which fail to see 
money’s worth in an expenditure to procure wholesome drinking- 
water for their people. It is surely a terrible consideration, that 
thousands may be slaughtered in a few weeks by a water com- 
pany through the shortsightedness and parsimony of those who 
have accepted the high office of guardians of the public health 
and wellbeing. That thousands have thus been recently de- 
stroyed in the east end of the metropolis is a matter hardly to be 
doubted by the unprejudiced thinker. Public feeling will no 
doubt before long obtain for London water fit to drink, as it has 
done for a few other large towns. But, then, “ before long ” 
cannot mean less than some years even in the mouths of the 
most sanguine sanitary reformers, and before that it is more 
than possible that impure water may bring upon the population 
a decimating epidemic. Hence the importance of the object of 
this article, suggested some time since to me by the editor of the 
Popular Science Review . This object is in effect to assist the 
reader in deciding how far means are within his reach of getting 
from a foul supply pure drinking-water for himself and those 
whose welfare is his more immediate concern. 
By pure drinking-water, it may be perhaps necessary to state, 
is not implied water actually pure. Eeally pure water is only 
