6 Mr. Waldie's investigations connected [No. 1, 



required subsequently ; afterwards the diminution is slower, or in 

 some cases even an increased quantity of oxygen may be required? 

 from changes taking place in the water causing the production of a 

 larger quantity of readily oxidisable matter. This therefore gives no 

 indication of the weight or actual quantity of organic matter present. 

 The weight of organic matter ascertained by experiment however, 

 indicates in some cases a rather rapid diminution at first. But this 

 is only to a small amount, except in the case of highly decomposable or 

 putrefying liquids, such as sewage or mixtures containing much sewage. 

 Calculation will show that the loss of weight of organic matter in 

 mixtures Nos. 1 and 2 is less than would have been sustained by the 

 constituent proportion of sewage water in them. In No. 3 probably 

 the vegetable matter of the Tank water added caused the more rapid 

 and extensive decomposition. 



The loss of weight in the mixture No. 3 is 3.4 grains in 8 days, 

 being fully more than half of the original amount ; in Nos. 1 and 2 

 it is only only 1.8 grains and 0.3 grain respectively. 



But the river water at no time could contain anything like the 

 proportion of sewage that these mixtures did, such as one-fifth, one- 

 eighth or even one-twelfth of sewage, the smell alone of such mixtures 

 makes the supposition quite inadmissable ; besides a comparison of the 

 size of the river with the amount of drainage of the town would show 

 that such a proportion was quite impossible. The amount of liquid 

 discharged by the drains compared with the volume of water in so 

 large a river must be insignificant. 



But instead of citing results of my own, which if incorrect may be 

 supposed to be all equally incorrect, it may carry more weight to quote 

 the results of others. The older determinations of organic matter are 

 generally of no value whatever, and I shall refer only to the most 

 recent and trustworthy. I have already quoted Dr. Frankland's results 

 with the London waters, but as all these are of water filtered for 

 distribution they may be considered not quite comparable. Another 

 example I shall adduce from the paper of Lawes and Gilbert 

 in the Journal of the Chemical Society already quoted. They give 

 tables of the composition of the Rugby sewage from May 1862 

 to October 1863, shewing that it contains in solution from 7.6 to 

 8.35 grains per gallon, and also a statement of the amount in the River 



