August 14, 1908] 



SCIENCE 



215 



paring it with tlie average of five of tlie lead- 

 ing foreign botanical journals it appears that 

 during the past two years the Gazette has 

 been giving 945 pages to their 648, 45 plates 

 to their 12; and 182 text figures to their 122, 

 while the average subscription price of the 

 foreign journals is thirty per cent, higher. 

 Accordingly after consulting with many bot- 

 anists as to what changes should be made to 

 equalize the Gazette with other journals of its 

 rank, the editors announce that since " the 

 pressure for publication is increasing rather 

 than diminishing " they will maintain the 80- 

 page size for each number, however gaining 

 additional space by " a more rigid selection of 

 original papers, a greater compression of these 

 papers in text and illustrations, a franker ex- 

 pression of opinion in reviews, and the aban- 

 donment of the department of ' News.' " With 

 these changes the publishers advance the sub- 

 scription price to seven dollars per year, a step 

 which is amply justified by the fact that the 

 Gazette will still cost far less per page and 

 plate than any of the foreign journals of its 

 rank. Botanists everywhere will be glad to 

 know of the groTfrth and development of this 

 American journal, and will wish it the con- 

 tinued success which it has earned so well. 

 Charles E. Bessey 

 The Univeesitt op Nebraska 



SPECIAL ARTICLES 

 an examination of the theorem op allen 

 hazen that for every death from typhoid 

 fever avoided by the purification of 

 public water supplies two or three 

 deaths are avoided from other 

 causes' 

 If Hazen's theorem is true, the purification 

 of polluted water supplies has sanitary and 

 economic consequences much more far reach- 

 ing than has hitherto been supposed. If, for 

 example, in the city of Pittsburg, purification 

 of the public water supplies by the new 

 municipal filters should, as may reasonably be 

 expected, effect a saving of at least one hun- 

 dred deaths a year from typhoid fever and, 

 according to the theorem, in addition two or 

 ' Preliminary communication. 



three hundred deaths from other causes, such 

 saving of human life means also the avoid- 

 ance of a present economic waste of two mil- 

 lions of dollars annually instead of half a 

 million from typhoid fever alone. 



Hazen's theorem rests upon the discovery 

 by Hiram F. Mills and others that in several 

 cities purification of the public water supply 

 has been immediately followed by a marked 

 decline in the total death rate, such decline 

 being far greater than that which would have 

 been effected by the decline in typhoid fever 

 mortality alone. It appears to have been first 

 definitely formulated and published by Mr. 

 Hazen in a paper on " The Purification of 

 Water in America," presented to the Interna- 

 tional Engineering Congress at St. Louis, in 

 1904. The theorem has not hitherto attracted 

 the attention or consideration which it de- 

 serves, and we have therefore critically ex- 

 amined the evidence upon which it rests and, 

 having found the theorem not only correct 

 but conservative, have gone further and un- 

 dertaken to discover precisely what are those 

 " other causes " of death in which the ex- 

 traordinary decline referred to takes place. 



For these purposes we have made an elab- 

 orate statistical study of the influence of the 

 purification of polluted public water supplies 

 in LoweU and Lawrence, Mass., upon the total 

 death rates of those cities, and also upon their 

 death rates from various diseases; comparing 

 the data for each city with those of the other, 

 and of both with similar data for Manchester, 

 N. H., a city of the same class which from 

 various points of view, such as location and 

 population, is remarkably well adapted to 

 serve as a norm. As a result of our studies 

 we have found that the theorem is true not 

 only for the cities mentioned, but also for 

 certain other cities, including Hamburg, Ger- 

 many, when this city substituted a pure for a 

 polluted water supply in 1893. We find, fur- 

 thermore, that the decline in total mortality 

 is accounted for to a large extent by the di- 

 minished number of typhoid fever deaths, but 

 to a much greater extent by a decline in 

 deaths from other causes; that about eighty 

 per cent, of the decline in general mortality 



