SYMPOSIUM OX SAXITATIOX 3 3 



form of purification will be necessary and this may vary all 

 the way from plain sedimentation to intermittent sand filtra- 

 tion followed by sterilization. 



The formula, of course, is intended to be used as a rough 

 guide and it is conceivable that there are instances where it will 

 not apply. Take, for example, the case of a very large stream. 

 where a sufficiently large factor of safety may be obtained 

 with the sewer outlet at a very short distance above the point 

 of water works intake, and on the same side <^i the stream : 

 here it is manifest, due to the impracticability of securing a 

 mixture of the sewage with the entire volume of the stream 

 that the sewage must receive treatement or the water works 

 intake must be extended to a point above or at any rate be- 

 yond the influence of the sewer outlet. As a rough guide, 

 however, such a formula may serve a useful purpose in nar- 

 rowing down the widely divergent practice of the present 

 time. 



Streams for Recreation Purposes 



Of recent years growing importance, is attached to the 

 maintenance of our streams for pleasure purposes. Every 

 summer there may be found scattered along the streams with- 

 in a radius of 50 miles or more of our large cities numerous 

 camps. This form of summer vacation is a comparatively 

 cheap and normally a healthful means of recreation. It ought 

 to be regarded as one of the means of improving the health 

 tone of our urban communities inasmuch as it is within the 

 means of so great a number of people. 



Under this head may be asked how high a degree of 

 4)urity should be demanded in a stream which is extensively 

 used for recreation purposes, but not for public water supply? 

 Within the last few years much emphasis has properjy been 

 placed upon the purification of sewage by dilution, which 

 after all. is purification by oxygenation in which a natural 

 resource is utilized instead of an artifically constructed puri- 

 fication works. It has generally been held and in most in- 

 stances rightly held that the degree of dilution necessary is 

 merely that which will prevent a nuisance, having reference 

 primarily to unsightly floating matter and bad odors. For 

 most rivers and many of the smaller streams of the country, 

 this requirement as to the cleanness of the waters is all that 

 is necessary. 



There is. however, a certain class of streams which be- 

 cause of the beauty of the country through which they flow 

 and their specially favorable location becomes highly prized 

 for camping and recreation purposes. It is a striking circum- 

 stance, in fact, that recreation seekers nearlv alwavs look for 



