July 10, 1885.] 



SCIENCE. 



29 



ness was occasionally mitigated by the action 

 of the pumps at Bridgeport, raising water from 

 the south branch into the canal as needed for 

 navigation, it was not until the spring of 1865 

 that it was finallj^ decided to deepen the canal, 

 as had been recommended in 1860. A remark- 

 able epidemic of erj'sipelas, which prevailed 

 exclusivel}^ along the south branch and main 

 river in 1863, and which was obviously caused 

 by the unspeakable filth of these streams, had 

 undoubtedly much to do in securing this de- 

 cision ; but the efficiency of this mode of relief 

 had been incidentally shown by the action of 

 the pumps at the head of the canal. The work 

 was begun in the fall of 1865, and completed 

 in July, 1871 ; but even before it was com- 

 pleted, the water-supply, taken from a point 

 about one-fourth of a mile from the shore, had 

 been so often affected by the current from the 

 river, that a tunnel under the lake, running out 

 two miles farther, was constructed, for the pur- 

 pose of getting the supplj" from beyond the 

 area of river-pollution. 



Reljing upon the deepening of the canal 

 to establish and maintain a cleansing current 

 from the lake through the river, the pumps at 

 Bridgeport were removed when the ' deep cut ' 

 was completed, notwithstanding which there 

 was for some time a decided improvement in 

 the condition of the river. Gradually, how- 

 ever, the increased sewage-production of the 

 rapidly growing city, a diminution of flow 

 through the canal due to various causes, and 

 the fluctuations of the lake-level, indicated the 

 necessity for further eflbrt.^ In 1871 the con- 

 struction of the ' Ogden ditch ' was begun ; and 

 after its completion another factor was added 

 to the problem, — a factor which acquired ad- 

 ditional importance, when the dam and flood- 

 gate intencled to regulate the flow through the 

 ditch were broken down, and became inopera- 

 tive. The Des Plaines pours through this ditch 

 into the south branch a volume often greater 

 than the entire capacit}^ of the canal. Every 

 cubic foot of this water reduces by so much 



1 The lake is highest in July and August, and lowest in De- 

 cember and January, the average fluctuation being about three 

 feet. Occasionally it is much greater than this : for example, on 

 one occasion in February, 1875, the stage of water at the head of 

 the canal was only five feet and eleven-hundredths, while for a 

 short time in April, 1877, it was fourteen feet. Local rains on 

 the watershed of the south branch, or on the area drained by the 

 summit-level of the canal, or high water in the Des Plaines 

 pouring into the south branch through the 'Ogden ditch,' — all 

 operate, to a greater or less extent, in the same way that a low 

 lake-level does; that is, the current in the south branch and 

 main river is suspended or reversed, and, instead of flowing off 

 through the canal, the sewage is carried into the lake in danger- 

 ous proximity to the intake of the water-supply at the ' crib.' 

 This condition obtains every spring for varying periods, and 

 during the spring just closed it was frequently observed. A 

 local rain on the 2d of this month (June) created a current from 

 the river, which continued for several days, the eff"ect being per- 

 ceptible for some distance beyond the ' crib,' until counteracted 

 by north-east winds. 



the inflow of the lake through the main river 

 and south branch into the canal, and thus 

 causes a concentration of the pollution. 



In 1881, after careful study of all the con- 

 ditions, I urged the re-establishment of the 

 pumping-works at Bridgeport, recommending 

 that their capacity be made sixty thousand 

 cubic feet per minute, and subsequently point- 

 ed out the necessity for the re-establishment of 

 the dam at the ' Ogden ditch.' An appropria- 

 tion was promptly made for the pumping-works, 

 and these were completed late in the fall of 

 1883 ; but thus far they have not pumped over 

 thirty-five to forty thousand cubic feet x^er 

 minute. Within a short time an appropriation 

 has also been made for the repair of the dam.^ 



At the present time the fouling of the river 

 and its branches from the blood, off'al, and 

 wastes of the slaughtering and packing estab- 

 lishments and their subsidiary indnstries, has 

 been materially reduced by the utilization of 

 much which was formerly considered worthless, 

 and consequently was thrown into the river or 

 upon the surrounding prairies. On the other 

 hand, the volume of sewage proper has in- 

 creased with the growth of the population and 

 the extension of the sewered area, until a daily 

 sewage-production, which may be roughly esti- 

 mated at from forty-five to fifty million gallons, 

 is now poured into the river and its branches. 

 With the exclusion of the waters of the Des 

 Plaines River from the canal, and the continu- 

 ous operation of the pumping-works, this sew- 

 age need never be allowed to find its way into 

 the lake, except for a short time during the 

 spring thaws, or as the result of unusual rain- 

 falls ; and these exceptional occurrences will 

 not then entail serious consequences, owing to 

 the permanently improved condition of the 

 river and its branches, resulting from the con- 

 tinuous removal of the sewage, and the cleans- 

 ing eff*ect of the steady influx of lake-water. 



It should be stated that provision is made 

 for the purification of the north branch of the 

 river, as originally suggested by Mr. Ches- 

 b rough, through a conduit from the lake, with 

 pumps capable of pouring eighteen thousand 

 cubic feet of water per minute into the branch 

 at Fullerton Avenue. To prevent this from 

 creating a current into the lake through the 



1 When this is completed, it may be necessary to convey the 

 flood-waters of the Des Plaines to Lake Michigan, at some point 

 north of the city, in order to obviate the danger of inundating 

 the town of Joliet by freshets from a watershed of some twelve 

 hundred square miles. This, however, and the treatment of 

 local areas, are matters of detail which present no features not 

 easily mastered; as, for instance, the fork of the south branch 

 which runs near the Union stockyards, now a foul cesspool. 

 To bring this within the general system requires that an ade- 

 quate volume of lake-water be poured continuously into the head 

 of the fork, washing its contents, properly diluted, into the 

 south branch, to be thence pumped into the canal. 



