T− t 1 + k (T − t) | T-t 1+'k (T − t) | T−t | 1 + k (T − t) | T− t 1 + k (T − t) 100 1.00284 180 1.00523 260 105 1·00795 340 1.00298 185 1.00551 265 1.00810 345 1.01079 1.00312 190 1.00566 270 1.00826 350 1.01095 1.01064 XI.-On the Composition, Value, and Utilization of Town Sewage. By J. B. LAWES, Esq., F.R.S., F.C.S., and J. H. GILBERT, Ph.D., F.R.S., F.C.S. Position of the Sewage Question. It is no less true than strange that, after so many centuries of advance in regard to almost every other requirement of civilised life, the lesson should not yet have been learnt of how to dispose of the excretal matters of large populations, in such a manner as to secure both their collection and removal without nuisance and injury to * The substance of this paper was given as a discourse before the Chemical Society, February 1, 1866, by Dr. Gilbert. health, and their economical utilization for the reproduction of food. But it is undoubtedly the fact that, hitherto, where utilization has been the most complete, comfort and health have generally been in the greatest degree sacrificed, and where, on the other hand, the refuse matters of town populations have been the most rapidly and perfectly removed from their dwellings, there has been either no utilization at all, or it has been most imperfectly attained. Sewage, the foul stream which flows through the underground veins and arteries of our great cities, carrying with it the excretal and other refuse matters of large populations, hitherto to little better purpose than to be wasted, and to be a source of pollution to our rivers to destroy their fish, injure their channels, and render them unfit as a water-supply to other towns-is the product of the, to us, modern, but in the history of the world only resuscitated and elaborated, water-system of town purification. There is no doubt that excretal and other refuse matters are removed from habitations more rapidly, with less nuisance to the occupants, and with less injury to their health, by means of water, than in any other way hitherto practised on a large scale. But such is the dilemma into which the progress of modern civilisation in this direction has brought us in this country, so far as utilization and the condition of our rivers are concerned, that some authorities, especially on the Continent, incline to the reactionary conclusion that a return to the cesspool system, or rather the adoption of some improved barrel, tank, or cesspool system, of collection and removal without admixture with extraneous water, is inevitable. Before, therefore, entering upon the question of the composition, value, and modes and results of the utilization of dilute town sewage, it will be well to call attention, though very briefly, to some of the results of experience hitherto attained, under other systems of town purification, and other modes of utilization of the products, than the modern ones by means of water. China and Japan are frequently cited as affording examples of very perfect utilization of human excretal matters, and, as a consequence, of great productiveness of the soil and great concentration of population on a given area of land. The manner of collecting, removing, and transporting human excretal matters in those countries is, however, such as to be quite inadmissible with our modern notions of cleanliness, decency, comfort, and health. It is frequently stated that in Belgium human excretal matters are very perfectly utilized, and realise considerable money return to the town populations. Indeed, in one of the applications made only last year to the Metropolitan Board of Works for the concession of the Southern sewage of the Metropolis, and still under the consideration of that body, it is stated that the excretal matters sell in Belgium for something over £1 per person per annum. There is no doubt that in some parts of Belgium the solid, and a portion of the fluid excrements of the town populations are collected, as free as possible from extraneous water, in receptacles of more or less perfect construction, and periodically removed for application to the land, and that the land so fertilised is very productive. From observation and inquiry made in some of the towns in question, it may, however, be safely affirmed, that the practices adopted are attended with, at any rate, so much of nuisance and discomfort as would not now be permitted in this country; whilst it would appear that a considerable proportion of the urine of the populations escapes collection and utilization. As the result of the same inquiries, it was concluded that, in no case, did the town population realise by the disposal of their excretal matters as much as averaged one frane per head per annum. The conclusion that, as a rule but little, and frequently nothing, is realised by town populations when their excretal matters are collected under more or less modified cesspool or tank systems, as free as possible from extraneous water, and so removed for application to the land, is fully confirmed by the results of an inquiry conducted by a Commission sent out by the Prussian Government in 1864, to investigate the modes of collection, removal, and utilization, in various localities, with a view to the adoption of improved plans for the city of Berlin. The Prussian Commissioners, Herren C. v. Salviati, O. Röder, and Dr. Eichhorn, visited and reported upon, not only the Belgium towns of Ghent, Ostend, and Antwerp, but likewise Hanover, Cologne, Metz, Carlsruhe, Strasburg, Basle, Lyons, Zurich, Munich, Nuremberg, Dresden, and Leipzig; and their report shows not only that the householders seldom realised anything like a franc per head per annum for their excretal matters, but that in the majority of cases it cost them something for the removal. Nevertheless, looking to the position and local circumstances of Berlin, and especially to the results of the water-system in this country hitherto, the Commissioners deprecate the adoption of that system for that city, and recommend more perfect arrangements and more stringent regulations for the emptying and removal of the contents of existing cesspools, and, where practicable, the adoption of a system under which the excretal matters of each house are to be collected in a barrel placed at the bottom of the shaft leading from the closets, which, when removed, is covered with a closely fitting lid, and is of such dimensions that two men can carry it by means of handles attached for that purpose. They seem to anticipate little, if any, pecuniary profit to the town from these arrangements, but consider that they will be attended with scarcely any, or even no, nuisance or discomfort, and that by their means a large amount of valuable manure will be provided in a convenient form for transport and utilization. There can, however, we think, be little doubt that under such a system the collection and removal must be attended with considerable nuisance, that the greater part of the urine will be lost, and that the cost of the collection, removal, and transport will be such as to render the utilization unprofitable beyond a comparatively limited distance from the city. There is little probability that the difficulties of the water-system will lead us in this country to have recourse again in our large towns to any system of cess-pools, tanks, or barrels, however improved; but it may be well here to notice one or two attempts that have been made within the last few years to obviate the use of water, and thereby to avoid the pollution of rivers, and to secure the collection of the manurial matters in a form more readily transportable by ordinary means, and, therefore, more applicable for general agricultural use: for there cannot be a doubt that if any system could be devised by which human excretal matters could be collected and removed from dwellings, without either nuisance or injury to health, and obtained economically in a concentrated, dry, and portable condition, their utilization would be much more perfectly attained by such means than is at all likely, or even possible, under the water-system. Perhaps the most noticeable attempt of the kind in question is that which has been made at Hyde, in Lancashire, a manufacturing town of more than 20,000 inhabitants. Some few years ago a company contracted to carry out what they call the "Eureka system." They provided boxes to fit in at the back of the privy or closet of nearly every house, leaving scarcely a water-closet in the place. Some disinfecting or deodorising mixture is put into the box before it is placed in its position, and the box is exchanged for a fresh one after a certain number of days, according to the number of individuals frequenting the place; and it is stipulated that neither extraneous water, nor any other than human excretal matters, should be accumulated in these receptacles. The boxes, when removed, are covered with closely fitting lids, and so transported in closed vans to a manure manufactory close to the town. Here the matters are first well mixed, and then strained to remove rags, which are washed and sold for paper-making. More disinfectant is then added, and the matter concentrated by distillation, the distilled water being sold to dyers and bleachers. The residue thus thickened is then mixed with coal-ashes, which are collected in the houses in casks left for the purpose, and before being used are re-burnt in a reverberatory furnace, and finely ground. On visiting Hyde in 1863, it certainly appeared that the mode of collection and preparation adopted was attended with, at any rate, very little unpleasant odour, and it was maintained by the advocates of the system, that its adoption had been successful in a sanitary point of view; though even at that time some difference of opinion existed, and a controversy on the subject was in progress. The system is still in operation; but we are informed that the feeling of the inhabitants is very strong against the maintenance of the works in the neighbourhood; indeed, that an injunction against them has been sought, though unsuccessfully, and that proceedings by indictment are now being taken. This opposition has reference not to the mode of collection, but to the conducting of the manufacture so near to the town, But, whether or not, the plan of collection and removal may have proved successful, so far as the avoidance of nuisance and injury to health are concerned, the process of manufacture seems, unfortunately, to offer but little prospect of successful utilization, so far at least as can be judged from the results of an analysis made at Rothamsted, of a sample of the manure obtained direct from the works. It was found to contain only between 1 and 2 per cent. of ammonia. Such a manure, although it might be useful enough when applied in quantities of many tons to the acre, would obviously be not worth more than its carriage beyond the distance of a very few miles. Besides, the great dilution of the more valuable manurial matters by the admixture with ashes, a little consideration of the habits of the people is sufficient to account for the small quantity of ammonia found in the manure; for it is obvious that little of the urine beyond that passed once a day with the fæces would reach the |