120 
EIGHTH REPORT. 
river water cannot be constantly safe for domestic consumption in its 
raw state. Were every one of these municipalities supplied with sewer¬ 
age systems, and were the most perfect sewage disposal plants installed, 
this water would still be unsafe for domestic uses. The natural drain¬ 
age from closely inhabited land is dangerous enough, but in addition to 
this there are those occasional and sometimes surreptitious pollutions 
which are doubly dangerous in themselves, and which inevitably occur 
whenever people live along the banks of a stream. If we review the his¬ 
tory of some of our classic typhoid fever epidemics, we will recall that 
the ultimate cause of those epidemics was just such isolated and com¬ 
paratively insignificant pollutions. The Plymouth epidemic, it will be 
remembered, arose from a single focus of pollution upon a sparsely in¬ 
habited drainage area. The conditions in connection with the New 
Haven epidemic were similar, as were those at Ithaca and Butler. No 
amount of city sewage purification would have prevented these epi¬ 
demics. The fact that there was habitation upon the drainage area was 
sufficient to cause the trouble. Therefore, the pollution of streams drain¬ 
ing occupied countries is inevitable and the water of all such streams 
is dangerous for domestic use in its raw state. The sooner we accept 
these facts, the more intelligently we can deal with the entire situa¬ 
tion. 
The admission that our streams must be polluted, does not, however, 
warrant the conclusion that they may, with propriety be abused. The 
inevitable pollution of any stream is a reasonable one. It does not 
affect any of the values of a water course, except that of domestic supply. 
Such pollution never reduces a river to a stream of liquid filth. It 
does not render the water a damage to industrial enterprises, nor 
does it kill fish, nor make the stream a general nuisance. The only 
.damage caused (that of domestic water supply) can readily be over¬ 
come by filtration, or similar methods of purification, and the cost of 
such purification systems and the expense of their maintenance must 
be considered as a reasonable price which society must pay in return 
for the advantages accruing by reason of the industrial and social de¬ 
velopment upon the drainage area. Surely this is not an unreasonable 
price. 
Therefore, it seems as though the. limit beyond which pollution of 
streams should not proceed is that defined by what may be considered 
as inevitable and reasonable pollution. Under such a limit no war¬ 
rant is given to cities to dump immense volumes of raw sewage into 
a river, nor is a manufacturing establishment justified in pouring out 
its millions of gallons of damaging wastes into the very streams which 
must be used for water supply by us and by generations yet unborn. 
Looking at the matter from this point of view, it is questionable whether 
or not an industry or a city is not justified in polluting streams up to 
a point which does not exceed the inevitable degree of pollution. Inas¬ 
much as it is necessary to purify stream waters for domestic consump¬ 
tion, it makes little difference whether or not the pollution be the 
natural contaminated drainage, or the partly purified effluent of a 
sewage disposal plant. When, however, the amount of pollution in¬ 
creases so as to make the purification of the water for domestic pur¬ 
poses more expensive or more uncertain, such pollution must be con- 
