THE RIVER IVANDLE. 



33 



is a turbine-wheel worked by the sewage itself. This is an hydraulic 

 apparatus not much employed in this country, though the celebrated 

 paper-mill at which the paper for the Bank of England notes is made 

 has been worked for years by a turbine. 



It is probable that ultimately Croydon will be compelled to dis- 

 tribute the sewage over higher grounds, where the subsoil is more 

 porous, as the effluvium is now sometimes offensive. 



The effect of land in absorbing the bad parts of sewage is very 

 remarkable. Professor Odling investigated the action on the Bed- 

 dington sewage grounds in November 1867. The sewage, amounting to 

 3)274,-300 gallons, had been distributed over 30 acres of land for two 

 days. Professor Odhng analysed samples of the affluent water taken 

 every quarter of an hour, of which the following is a summary : — 



Analysis of Sewage of Croydon, Nov. 24, 1867. 



Total solid residue . 

 Mineral matter . . 

 Volatile matter . . 

 Chloride of sodium 

 Ammonia . . . . , 

 Nitrogen as ammonia, 



Oxides ... 



Organic matter 



The River -Wandle is not immediately affected even by heavy rain- 

 falls ; nevertheless, it has occasional risings. 'In the year 1866 one of 

 my family returned from Wallington, saying that I should be much 

 astonished when I visited the garden, as indeed I was. Instead 

 of the usual peaceful flow of water in the river, the rush was 

 largely increased ; the retaining walls of the backwater were under- 

 mined, and the earth was rapidly being washed away: so what was 

 the matter .? " The Bourne was down." 



D 



