180 



THE FARMER'S MAGAZINE. 



TO WHAT IS SEWAGE APPLICABLE? 



BY CUTHBERT W. JOHNSON, ESa., F.R.S. 



The report of the three engineers, ap])ointed by 

 our Government to examine the plan of M. Bazal- 

 gette for the main drainage of London, has just 

 appeared. Adopting the general outline of the 

 plan proposed by the engineer of the Metropolitan 

 Commissioners, they advise the construction of 

 much larger, far more extensive works. They 

 suggest that trunk sewers should be formed 

 capable not only of taking away the present 

 amount of London sev.'age, but that they should 

 be capacious enough to receive that of a future 

 London, and also the large amount of ordinary 

 rainfall. This bold and comprehensive view will 

 probably be carried out; it will most likely end in 

 the outlet for these main-trunk sewers being placed 

 nearly, if not quite, on the sea shore. To reach 

 this distance, and to ensure a sufficiently rapid 

 flow, higher levels than those once suggested will 

 most probably be necessary; more powerful steam 

 engines will be needed. Such an arrangement will 

 not be without still greater interest to the farmers 

 of Essex and Kent. The more elevated the bed of 

 the sewer, the more easily are its contents rendered 

 available for irrigation, and there is abundance of 

 grass land, between the metropolis and the German 

 ocean, to profitably employ and deodorise all the 

 sewage produced by even far more than 2,000,000 

 of inhabitants. I would most earnestly impress the 

 importance of these considerations upon those who 

 will have the construction of these huge drains ; 

 my own opinion rather inclines towards a direct 

 line of trunk sewers towards the sea. I am aware 

 that immediately bordering the Essex shores of the 

 German ocean, there are marshes of such sufficient 

 magnitude as to employ all the great mass of foul 

 waters with which we have to contend. It is here 

 that we find those extensive sweeps of marsh land 

 so placed, as to be inifit for the habitation of man ; 

 here there are no dwellings congregated in villages, 

 nor even solitary farm-houses ; they have the open 

 water for a boundary ; they are below the level of 

 the sea at high tide; they many of them rest on 

 substrata of sand or gravel, of all sites the best for 

 that imderdrainage so essential to the successful 

 irrigation of grass. 



The proposed employment of this sewage 

 in agriculture has given rise to considerable 

 discussions as to its being adapted for watering 

 arable soils, especially to those bearing the cereals. 

 The arguments have been carried on with an abun- 



dant verbiage, and a zeal which but too often barely 

 escaped being offensively personal, and often totally 

 neglectful of certain well known agricultural facts, 

 which must modify severalbroad assertions hazarded 

 during the controversy, and render others very 

 inapplicable in our climate. 



It must be remembered on all occasions, in any 

 proposed irrigation, that when we'are watering the 

 soil, the liquid employed is either for the mere 

 water it contains, or for the impurities dispersed 

 through it, or for both. Now it happens,* in the 

 case of the grasses that the rainfall in our climate is 

 not sufficient to produce a maximum amount of 

 growth. We can trace the effect of varying 

 amounts of moisture in travelling from the driest 

 to the wettest side of our island. The produce of 

 the pastures of Norfolk will, in this respect, bear 

 no comparison with those of Shropshire and Here- 

 fordshire. The sandy soils of Cheshire yield an 

 amount of grass which would be reduced to mere 

 sheep-walks, if they were transferred under the far 

 less rainfall of Suflfolk. The moist climate of the 

 west of England accounts for this widely different 

 value of the pasturage ; still the most copious rain- 

 fall of even western England fails to pi'oduce the 

 maximum amount of grass; more water may be 

 still profitably applied to the meads. The West of 

 England farmer acts upon this conviction and upon 

 this experience. He forms water-meads ; he 

 employs in need even the purest waters — meaning 

 by that, water nearly free from earthy matters, 

 springs which are just bubbling out of the chalks of 

 the vale of the Itchen, or the Kennett, or the 

 equally bright spring waters of the oolite in the 

 vale of Wardour. And mark how copiously he 

 applies that nearly pure water. Note what Mr. 

 Combes, of Chicksgrove, said at the Salisbury 

 Meeting, when speaking of the fine water-meads of 

 the banks of the Wiltshire Avon. " The average 

 quantity of u-ater used for irrigating these mea- 

 dows," he observed, "is about 2,000 gallons a 

 minute per acre." And he adds, in another por- 

 tion of his valuable communication — a lecture the 

 more valuable as coming from a first-rate practical 

 authority — " A good flow of water, or what is called 

 thick watering, is always to be preferred to that 

 of thin watering, especially during the summer 

 months ; for a very thin watering for a week or 

 more together, at summer time, especially on a clay 

 soil, is oftentimes injurious. I may here remark 



