TKANSACTIONS OF SECTION G. 8G3 



may be taken at, say, 2*. per ton. Then we bave Is. 2d. per ton as the net value 

 of the refuse -when burnt on this system. A rougrh outline scheme is described for 

 the burning of London sludge at Barking and Crossness when mized with ashbiu 

 refuse barged down by steam power. 



Sites for destructors in special reference to areas of cartage and population are 

 dealt with, and also a calculation is given showing how the refuse of any com- 

 munity is sufficient to provide it with electric light at no extra cost beyond that 

 now involved in refuse disposal. Village refuse is also treated briefly, and united 

 action of sanitary engineers to bring about the general adoption of the combustion 

 system is urged. 



4. The Alsorption and Filtration nf Sewage on Sandy and other Soils. 

 By RiCHAED F. Grantham, M.Inst. C.E., F.G.S. 



The author refers to the remarkable results of the experiments conducted for 

 the last two years at St. Lawrence by the Massachusetts Board of Health upon the 

 filtration of sewage. 



The results are compared with instances of sewage farming upon sandy soils. 



The examples of sewage irrigation at Edinburgh, Dantzig, and Berlin are 

 described, and the effect upon the sandy soil in each case, as well as the average 

 quantity of sewage treated per acre per day, is alluded to. 



The particulars of the iilter tanks constructed and the materials used by the 

 Massachusetts Board in their experiments are stated, and a table is given to .show 

 the quantities treated and the effect upon the nitrogenous matter. 



The tanks were 6 feet deep, built water-tight; 17 feet 4 inches in diameter at 

 the top and 16 feet 8 inches at the bottom. Two-inch drain-pipes and a thickness 

 of a foot of gravel and sand, decreasing in coarseness upwards, were laid and spread 

 at the bottom. Above this layers of sand and of gravel and othei- materials were 

 placed in several tanks. The sewage was delivered on to the surface of the filters 

 intermittently. 



The volumes of sewage dealt with in sewage farms are contrasted with the quan- 

 tities experimented upon, and Dr. Frankland's experiments for the Eivers Pollution 

 Comniissioners are shown to corroborate the results of the Massachusetts Boards 

 investigations as regards the quantities and degree of purification. 



The action of the filters is shown to be not merely straining the sewage, but in 

 consuming and destroying the organic impurities, and this action is due to the 

 presence in it of organisms which require a supply of oxygen for their existence 

 and multiplication. The interstices in the sand and gravel afford air-spaces for 

 these organisms to multiply ; but top soil and mould retain so much moisture that, 

 although the bacteria are filtered out, a large percentage of albuminoid ammonia is 

 left in the effluent. 



From the quantity of sewage disposed of on the Berlin sewage farm per acre 

 and from that ordinarily absorbed by intermittent downward filtration are calcu- 

 lated the areas of land that according to the same ratios would be required for the 

 disposal of the London sewage, and these are compared with the space required for 

 the volumes according to the ratio shown by the experiments. 



It is suggested that there would be no difficulty, from the nature of the forma- 

 tion of the Maplin and Foulness Sands, in reclaiming and underdraining them and 

 laying them out for filtration areas. 



5. Shield Timnellinq in Loose Ground under Water Pressure.^ 

 By G. F. Deacon.— See p. 532. 



6. Proposed Forth and Clyde Ship Canal. 

 By David A. Stevenson, B.Sc, F.B.S.E., M.Inst.C.E. 



The route that has been proposed by Messrs. D. and T. Stevenson, civil 

 engineers, Edinburgh, passes up the valley of the Forth from Grangemouth by 



' Ordered to be printed in cxtenso. 



