NA TURE 



157 



THURSDAY, DECEMBER 27, 1877 



THE METROPOLITAN SEWAGE 



THE question of the effect of the main outfall sewers 

 of the metropolis on the reaches of the Thames 

 below London has occupied the attention of engineers 

 rot only since the completion of the works, but through- 

 cut the long series of years when those works were under 

 consideration. Some persons qualified to make accurate 

 observations and draw correct deductions from them, 

 asserted that large masses of deposit were directly due to 

 these outfalls, and were daily increasing in magnitude, 

 while others, demanding equal confidence in their state- 

 ments, asserted that no such deposits existed— in fact, 

 that the sewage outfalls tended to improve the bed of the 

 river by increased scour ; thus the bulk of engineers for 

 a long time held diverse views or suspended judgment on 

 the subject, while the general public, not knowing whom 

 to believe, trusted it would turn out all right in the end. 

 Inasmuch as the Metropolitan Board of Works is bound, 

 under the Thames Navigation Act of 1870, to keep the 

 Thames free from banks and other obstructions to the 

 navigation due to the flow of sewage from their outfalls, 

 and to carry on all dredgin g operations required for that 

 purpose, at their own expense, the vision of the possible 

 cost of these works to the London ratepayer is unlikely 

 to be pleasing ; still less could any interference with the 

 highway to the most important port in the world be 

 tolerated by the Board who were looked to for its preser- 

 vation. In 1869, the metropolitan main outfalls having 

 been opened in 1863-64, the Home Secretary appointed 

 Mr. Rawlinson to hold an inquiry on the reported silting 

 up of the Thames, which was then causing great alarm ; 

 such, however, was the contradictory nature of the evi- 

 dence, that the result was almost nugatory, and the ques- 

 tion still remained in abeyance. In the course of the last 

 summer the Thames Conservators requested Capt. Calver, 

 R.N., F.R.S., to direct his attention to the subject, and 

 report to them thereon. Before pointing out the conclu- 

 sions arrived at by Capt. Calver,^ it will be as well to 

 direct attention to the part of the river under considera- 

 tion. The northern outfall is situated immediately above 

 Barking Creek, which forms the embouchure of the river 

 Reding, and is about two miles below Woolwich ; the 

 southern outfall is about 2\ miles lower, or 4^ miles below 

 Woolwich. 



In the face of the fact that this special inquiry was held and 

 many competent witnesses examined with the sole object 

 of determining whether or no the sewage outfalls have 

 caused a silting up of the river in their neighbourhood, or 

 i the formation of shoals and mudbanks, and that so many 

 j observations and statements have since been made with 

 the same view, it seems perfectly monstrous that the 

 quesiion should still remain unsettled. In the report now 

 before us we have the last contribution on the subject, or 

 perhaps, with more fairness it might he said the last but 

 one, as since its publication Sir Joseph Bazalgette has 

 addressed to the daily press a letter containing a direct 



« " Report upon the Discharge of Metropolitan Sewage into the River 

 Thames at Barking Creek and Crossncis." By Capt. E. R. Calver, R.N., 

 F.R.S. 



Vol. XVII.—- No. 426 



denial of many of the conclusions thete arrived at. When 

 professional experts differ so entirely not only in their 

 conclusions, but also in the facts upon which these con- 

 clusions are based, we see no other course open but to 

 appeal to the cooler and more unbiased judgments of 

 pure science. 



In comparing the analyses of Thames mud from various 

 parts of the river, given in Capt. Calver's report, em- 

 bodying a series taken in 1867, and another in 1868, by 

 the late Dr. Letheby, with those given by Dr. W. A. 

 Miller, and Dr. W. Odling in 1869, so close an agreement 

 is manifest that a safe conclusion can be drawn from 

 them. The analyses are as follows :— 



Average Percentage Composition. 



Organic matter 1500 14-19 1867 Dr. Letheby. 



Mineral „ 8500 85-81 1868 „ 



10000 100 'OO 

 On these analyses Dr. Letheby remarks that the above 

 percentage proportions did not differ materially from the 

 quantities of organic and sewage matters which he found 

 suspended in water at London Bridge, and in the mud at 

 London Bridge, Chelsea, and Westminster, when the 

 sewage was discharged at low water. The next table 

 gives nearly identical results from the analysis of the mud 

 at the outfalls in 1867, and those of the suspended matter 

 in the Thames water at Greenwich, Woolwich, and 

 London Bridge in 1862, by the same chemist. Now, Dr. 

 W. A. Miller so far agrees with these results that in his 

 evidence, given at the inquiry before referred to in 1869, 

 he states the percentage of organic matter in the mud 

 taken from Barking Creek to be i6-2, from the Thames 

 between Chiswick and Westminster, 158, and further, 

 that of these two quantities 3-1 and 3-05 respectively con- 

 sists of nitrogen, and finally, in answer to the question : 

 " But there is nothing special and differing in the mud 

 at Barking from the ordinary mud of the River Thames ? " 

 he says : No, the composition is as nearly the same as 

 may be. With these observations Dr. Odling's evidence 

 closely agrees. 



Here, then, we have an agreement which nobody 

 appears to dispute, and which leads inevitably to the con- 

 clusion that the great bulk of noxious putrescible matter 

 left uncovered at low water throughout the whole of the 

 tidal portion of the Thames owes its deleterious character 

 mainly, if not entirely, to the presence of sewage matters. 

 Having carefully pointed out and established this 

 identity of composition, Capt. Calver proceeds : " It is, 

 however, equally necessary to prove that there is enough 

 of this material in the sewage discharged from the out- 

 falls to account for the large accumulations of it which 

 have found a resting-place in the Thames channel." Here 

 we are met by estimites differing in the wildest manner, 

 and varying from 35 to 100 grains per gallon, and again 

 to neariy double that amount, but fortunately we are here 

 even given material for a trustworthy estimate. In the 

 table of analysis given by Prof. WiUiamson of samples 

 taken from the northern outfall in September of this year 

 we find io8-oi and 15 1*45 grains per gallon as the actual 

 amount of suspended solid matter at different times, 

 the samples being collected in fine weather. Now 

 abundant evidence has been given at various times, show- 

 ing that after heavy rain the sewage contains an amount 



