过滤的必要性
为什么城市和城镇应该过滤他们的水（经济考虑显然最困难的理解）
不久前，我收到了Fire and Water Engineering的请求，写一篇带有上述标题的简短文章，并毫无意义地同意。Setting my thoughts on the matter the “Why’s” seemed to me so numerous and obvious, that to take valuable space in a discussion of a subject that has been so ably set forth in numerous articles and papers by others, was not justified, and I was about to dismiss the matter, with this suggestion to the Editor. It happened, however, that as J was about to do so I received two letters from two engineers from widely separated sections, each requesting similar information as to the possibility of purifying the water supply of their cities, in each case referring to a stream better than the average in its natural condition.
