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



gation, I cannot of course dispute it directly, but I state 

 most emphatically, that if the river bed were of the same 

 composition as it is at the present day, and if the vegetable 

 dyes &c., turned into the river then, were at all like 

 those turned into the river to-day, it would be almost 

 impossible for sulphuretted hydrogen to be given off in the 

 form of gas from the water, because it is now a well-known 

 fact that the oxide of iron largely present in the mud of the 

 Irwell and its tributaries, coupled with the large amount of 

 iron present in solution in the water (derived from dye- 

 works, chemical works, paper works, &c.), combines with it 

 when in the " status nascendi,'' forming ferrous sulphide. 

 This black compound enters largely into the constitution of 

 the mud of sewage-polluted streams, and I know from a 

 long series of examinations of the mud of the Irwell at 

 Throstle Nest^ that ferrous sulphide is largely present in 

 the mud. 



I have analysed repeatedly, at various times in the year_, 

 gas collected from the Irwell at spots immediately above 

 the weir at Throstle Nest, below it at the place where all 

 the water samples were taken during 1883, 1884, 1885^ 

 and at Barton above the locks. At the first- mentioned 

 locality an immense evolution of gas is to be often seen 

 during the summer months, but I can say without hesita- 

 tion that it contains no trace of sulphuretted hydrogen, 

 having tested it many times for that gas, and never detected 

 the slightest trace. The gas thus rising to the surface 

 varies very much in composition at different places. That 

 coming to the surface at the Throstle Nest weir containing 

 a large quantity of carbon dioxide and a small quantity of 

 '^ marsh gas "^ (CHJ, whereas the gas rising near Barton 

 often contains nearly 60 per cent, of " marsh gas,""^ the rest 

 being mostly carbon dioxide. The river water is nearly 

 saturated with carbon dioxide gas (at the atmospheric 

 temperature), a very bad state of things, because it prevents 



