250 DR. C. A. BURGHARDT ON THE POLLUTION OF 



before being joined by the Tottington Brook) in Table 

 " C/' it will be at once seen that the Irwell is a pure 

 stream in comparison. 



I have analysed other small streams flowing through 

 Bury into the Irwell, and found all were largely polluted 

 with manufacturer's waste water. Between the junction 

 of the Roach and the Irwell there is a pollution of the 

 Irwell by the River Croal, This river is formed by the 

 junction of several brooks, of which the principal is the 

 Bradshaw Brook, flowing near Bolton. This brook — and, 

 in fact, all of them — are largely polluted with manufac- 

 turer's waste waters and sewage, but all of them are much 

 purer than the Irwell at the Salford boundary. From 

 my examinations of the river, and the curves plotted from 

 the weekly analyses of 1884, compared with the analyses 

 of 1885, I cannot draw any other conclusion than this : 

 that about One-half the total pollution of the Irwell, 

 before it arrives at the weir at Throstle Nest, is due to 

 manufacturer's waste water — in other words, to avoidable 

 pollution. This conclusion is supported by looking at the 

 oxygen curves produced by calculating on 100 parts of 

 the total matters in solution (Curve No. 6). It will be 

 seen that there was a continuous rise in the amount of 

 oxygen required to oxydize the organic matter in 100 

 parts of the total soluble matters, owing, no doubt, to the 

 long drought in 1884 (extending from March to July4thj 

 see rainfall in Table " A ") ; but suddenly, on June bth, the 

 curve drops from about 47 grains to 22. This diminution 

 is due to the whole week being a universal holiday in 

 Lancashire, viz., Whit-week. The same fact is observed 

 on examining Curve No. 6 (for the Christmas and New 

 Year holidays in 1884-85) in quite as striking a manner. 

 Again in the Easter holidays and Whit-week in 1885 the 

 same improvement is observed, proving conclusively that 

 the pollution of the river is very much less M'hen manu- 



