650 



SCIENCE. 



[N. S. Vol. XIV. No. 356. 



The self-purification of streams has been for 

 many years a perennial subject of discussion 

 among sanitarians. Early faith in the power 

 of running water to purify itself was severely 

 shaken by the advent of the science of bac- 

 teriology, and the postulate that ' no river 

 was long enough to purify itself was accepted 

 by many as representing the ultimate con- 

 clusion of science upon the subject. Recently 

 data have been accumulating in the opposite 

 direction and apparently indicate that under 

 certain conditions streams do tend to become 

 purer as they flow. A notable instance of this 

 may be found in a report just issued by the 

 Illinois State Board of Health on the Sanitary 

 Investigations of the Illinois River and its 

 Tributaries, with special reference to the efifect 

 of the sewage of Chicago on the Des Plaines 

 and Illinois rivers prior to and after the open- 

 ing of the Chicago drainage canal. 



Advance notes upon the same subject, issued 

 in 1900, gave the results of chemical and 

 bacteriological examinations of samples of 

 water at various points on these streams be- 

 tween Chicago and the Mississippi made during 

 the summer and autumn of 1899, before the 

 opening of the drainage canal. The present 

 report gives, in addition to the figures then ob- 

 tained, the results of further examinations 

 made in 1900 with the drainage canal in use. 

 The work was conducted by the State Board of 

 Health, under the direction of Dr. John H, 

 Long, professor of chemistry, Northwestern 

 University Medical School, and Mr. Jacob A. 

 Harman, civil engineer, of Peoria. Dr. Long 

 was assisted in the qualitative bacteriological 

 work by Professors F. Robert Zeit and Gustav 

 Fiitterer, of the Northwestern University Medi- 

 cal School. The reports of these gentlemen 

 are prefaced by an introductory chapter of 

 thirty-four pages by Dr. James A. Egan, secre- 

 tary of the Illinois State Board of Health, upon 

 the ' Pollution of the Illinois River as affected 

 by the Drainage of Chicago and other Cities.' 

 This contains a historical sketch of early in- 

 vestigations of the river, a compilation of 

 various opinions upon the self-purification of 

 streams and a summary of the results obtained 

 by the recent investigations. 



Dr. Long's report of the chemical and 



bacteriological examinations occupies seventy- 

 seven pages and that of Mr. Harman, entitled 

 ' A Preliminary Sanitary Survey of the Illinois 

 River Drainage Basin,' one hundred and five 

 pages. They include tables showing popula- 

 tioa, rainfall, stream gaugings, water-supply 

 and sewerage statistics, analyses, etc. The 

 brief report by Professors Zeit and Fiitterer 

 describes the various species of bacteria found 

 at each station, with special reference to their 

 pathogenic qualities. 



The most interesting feature of the report is 

 naturally the comparison of the condition of 

 the Illinois River before and after the opening 

 of the Chicago drainage canal. In order to 

 appreciate this a knowledge of the local condi- 

 tions is necessary. For many years the bulk of 

 the sewage of Chicago has discharged into the 

 Chicago River, a small stream with north and 

 south branches uniting in the heart of the city 

 to flow into Lake Michigan. This has been a 

 menace to the public water supply, which is 

 taken from the lake, and in order to lessen the 

 danger a pumping station was established at 

 Bridgeport in 1865, by which the water from 

 the polluted south branch was pumped into the 

 Illinois and Michigan canal, whence it found 

 its way westward into the Illinois and Missis- 

 sippi Rivers. This not being suflBcient to re- 

 lieve the situation in Chicago a drainage canal 

 was designed to connect the Chicago River with 

 the Des Plaines River, which is one of the 

 streams which unite to form the Illinois River. 

 A western outlet to Lake Michigan was thus 

 provided, which naturally changed the current 

 in the Chicago River. After ten years of con- 

 struction the canal was opened on January 17, 

 1900. Prior to this from 30,000 to 50,000 cubic 

 feet per minute was pumped at Bridgeport, and 

 it has been estimated that in 1899 this contained 

 from 85 to 90 per cent, of the total sewage of 

 Chicago. Since the opening of the canal the 

 actual amount of sewage sent westward has 

 increased, but the amount of water has in- 

 creased in a far greater ratio, the law requiring 

 a minimum flow in the canal of 300,000 cubic 

 feet per minute. According to Dr. Long's re- 

 port the increased dilution thus brought about 

 has resulted in an improved condition of the 

 sanitary quality of the water in the Illinois 



