TRANSACTIONS OF THE SECTIONS. 



33 



IV. The chemical condition of the Water of Leith, and the lakes connected there- 

 ■witli, as thoy recei^-e successive quantities of sewage from 180 drains and sewers 

 ■which discharge their contents into the stream at intervals from Coltbridge, west 

 of Edinburgh, down to the harbour of Leith. 



y. The analyses of the deposits of organic matter which are found in large 

 quantities in the bed of the Water of Leith after the entrance of the sewage, and 

 especially in rocky pools and above the dams ; as also of the sediment in the Lades 

 and in the harbour of Leith. 



VI. The chemical nature of the gases evolved in large quantities from the putre- 

 fying sedimentary deposits in the Lades and Water of Leith, including the harbour. 



VII. The natm-e and proportion of the gases dissolved in the waters of the river 

 above and below the influence of the sewage. And 



VIII. The degree of impurity in the atmosphere in the immediate neighbourhood 

 of the Water of Leith conveying sewage, and including the open sewers, the Lades, 

 and the harbour of Leith ; and contrasting the air under the influence of the foul 

 sewage and Water of Leith with the air in the centre of Edinbm-gh and Leith, and 

 away from the immediate influence of sewage. 



The author stated that the special part of the inquiry to which he wished to direct 

 the attention of the Section was the proportion and nature of the gases dissolved in 

 the waters which were contaminated mth sewage, as contrasted with those which 

 were uucontaminated by sewage. This department of the inquiry, in relation to the 

 contiunination of rivers by the sewage of towns, had not received that amount of 

 attention which it apparently deserves. The presence of oxygen gas dissolved in 

 natural waters aids in the decomposition of any organic matters which may pass 

 thereinto, and all healthy waters contain an amount of oxygen dissolved therein 

 which is equivalent to abont 29 per cent, of the entu-e volume of the gases in solution. 



The following Table gives the proportions of the gases present in one imperial 



