CHAMBERS'S INFORMATION FOR THE PEOPLE. 



unfiltered state we cannot depend upon sewage 

 going down and up again, and so passing over 

 a valley. Great part of the solid matter can also 

 be removed by this process, common house-ashes 

 being the best mixing and deodorising material 

 to facilitate the stuff being carried away. 



A piece of land should then be sought out, with 

 a slope, if possible, of one foot in 50, and the 

 filtered liquid, which will be still rich in fertilis- 

 ing ingredients, conveyed either by pumping or 

 gravitation to the highest point of that land. Iron 

 pipes should not be used, if possible ; but when 

 the land to be irrigated is very flat, they must be. 

 From the highest point of the land selected, the 

 liquid must be conducted, by open channels or 

 through common drain-pipes laid on to the sur- 

 face, to all the different points where it is wished, 

 and utilised for irrigation. The land adopted 

 should be moderately porous, and then for every 

 100 people an acre may be allowed, but this 

 varies much according to the nature of the soil. 

 The land must be thoroughly drained and pre- 

 pared. The best crops to be grown are Italian 

 rye-grass, with alternately crops of vegetables, 

 such as potatoes, cabbages, rhubarb, mangold. 

 All these will luxuriate on the liquid, and we 

 think we may say that the command of such 

 liquid would be worth to any person from ^5 to 

 ^10 an imperial acre, according to local circum- 

 stances. 



When a sufficient area of land cannot be pro- 

 cured for full irrigation, purification may be 

 secured, so far as we know, for a time at least, 

 by what is called ' intermittent filtration.' This 

 consists in letting the sewage liquid flow over 

 the irrigation beds for six hours, and leaving them 

 for the rest of the twenty-four to drain and 

 imbibe air. The organic matter retained in the 

 soil is by this means oxidised, and the absorbent 

 power of the soil is thus revived and ready to 

 receive a fresh dose. The mode of operation will 

 be easily understood by the following quotation 

 from the Fourth Report of the Rivers Pollution 

 Commissioners (1872) : 



' Irrigation and intermittent filtration have been 

 already named as methods capable of purifying 

 the foul liquid discharges from town-drains to a 

 satisfactory extent. With regard to the latter of 

 these processes, which was initiated in our chemical 

 laboratory, and there proved to be a most efficient 

 mode of purification, we have now to report that 

 it has been applied for eighteen months to the 

 whole of the sewage of Merthyr-Tydvil. Twenty 

 acres of a porous soil, drained from five to seven 

 feet deep, have been here arranged by Mr J. Bailey 

 Denton, C.E. in four series of beds, and over each 

 series in succession the drainage-water from a 

 town of 50,000 inhabitants, more than one-third of 

 whom are connected with the sewers, is poured 

 for six hours at a time. The beds are laid out 

 with a sufficient slope to carry the sewage (gradu- 

 ally sinking as it flows) from one side to the other 

 within the allotted time, being thus irrigated from 

 a nearly horizontal channel along the upper edge 

 of each ; and each being left to drain and become 

 aerated during eighteen hours of every day, they 

 bring into successful operation the process of 

 intermittent filtration on a very extensive scale. 

 These beds are, moreover, cultivated, and large 

 crops of cabbages have been grown on them. 

 These works have been carried out under an order 



510 



of the Court of Chancery, directing the Merthyr 

 Board of Health to abate the nuisance which the 

 sewage of their town was creating in the river, and 

 appointing Mr Bailey Denton to direct the neces- 

 sary works. They were designed by Mr Denton 

 expressly for the purpose of realising on a large 

 scale the results of that process of intermittent 

 filtration which had been devised and investigated 

 in the laboratory of this Commission ; and we have 

 twice inspected them, and on both occasions have 

 found the effluent water purified to an extent much 

 beyond that required by the standards of purity 

 suggested by us as those below which refuse liquids 

 should not be permitted to enter rivers. 



' The experience of these filter-beds at Merthyr 

 has made plain, what the experiments in our 

 laboratory had previously established, that towns 

 can cleanse their sewage upon a much smaller 

 area, or rather within a much less quantity of land, 

 than any experience hitherto of sewage irrigation 

 had led them to expect. Two processes of sewage 

 purification by the use of land are thus now open 

 to them, both of which have been sufficiently tried 

 upon a working scale. They will, no doubt, 

 endeavour to obtain a large extent, as heretofore, 

 wherever land conveniently situated and of suit- 

 able contour is to be had cheap, and they will then 

 irrigate with such a quantity of sewage per acre as 

 will enable them to realise the largest possible 

 returns from the cultivation of irrigated crops. 

 Where, however, the only land available is costly, 

 or its configuration is unfavourable for irrigation, 

 they will prepare a smaller area by deep and 

 thorough drainage of the subsoil, and accurate 

 formation of the surface, for the reception of much 

 larger quantities of sewage per acre, and seek, by 

 carefully carrying out the process of intermittent 

 filtration, to insure the perfect oxidation and de- 

 fecation of their now offensive drainage-waters. 

 It is, of course, only where irrigation is conducted 

 in the less intensive manner, upon the larger area 

 with the smaller quantity of sewage per acre, that 

 any hope can be entertained of an adequate return 

 for the money invested, although even a mere 

 filter, wherever the liquid cleansed by it is in itself 

 of a fertilising nature, is by no means necessarily 

 without some return, since at Merthyr-Tydvil Mr 

 Bailey Denton has shewn that healthy and luxuri- 

 ant crops can be grown upon it' 



How long the soil will continue to act in this 

 manner is at present unknown. Vegetation, it is 

 known, will thoroughly purify foul liquid, but the 

 inert earth may not have unlimited powers in that 

 capacity. 



On the whole, although we have made con- 

 siderable progress in this science, much labour 

 and thought must be bestowed upon it before safe 

 conclusions can be drawn applicable to all cases. 



BATHS WASH-HOUSES. 



Referring the reader to the article on the 

 PRESERVATION OF HEALTH for the sanitary 

 value of personal ablution, we shall here treat of 

 baths as a social arrangement, and of the various 

 mechanical appliances requisite for the establish- 

 ment of a system. 



