SEWERAGE, the method of removing superfluous water, rain, filth, night-soil, and other refuse matters from a town or other locality.
The subject connected with this article, is of very con siderable importance, as it affects the health, morals, and social well-being of the community ; as it is now universally allowed, that the accumulation of refuse matter is dangerous to health, and especially in crowded and densely-populated districts, where it is certain to encourage, if it does not generate, various kinds of epidemic disease ; besides which, it discourages habits of cleanliness, and so affects the morals of the lower orders. It is a matter which formerly was not sufficiently attended to •' but has of late years forced itself upon public notice, and is at the present day receiving that amount of consideration which it so well deserves.
Although, however, the matter has been widely canvassed, and much elaborate investigation entered into, we regret to say, that hitherto, mere matters of detail have received com paratively more attention than they deserved, and general principles have been too much overlooked; not that we would for a moment undervalue the investigation which is being carried on with reference to minutim, which are indeed of the utmost importance ; but we think that general principles should have had the first place in the order of investigation. Be this as it may, we must confess, that much useful and practical, as well as theoretical knowledge, has been eliminated by the process, mid many improvements introduced which are of considerable public benefit. This branch of professional practice is as yet in its infancy, and we may hope that a few years will add considerably to our practical and theoretical acquaintance with it, when theories, which are now only upon trial, shall have been fully and fairly tested, and some further inquiry entered into with respect to the object's which are sought after, in laying out the drainage of a town.
In considering this subject, a question naturally arises at the very outset, as to the objects to be effected by proper drainage of any locality. Now, formerly the object, for there was but one, was very well defined, and very simple ; it was this, to remove the refuse from the neighbourhood of inhabited districts, so that it might not become prejudicial to the health of the inhabitants. Within the last few years, however, some new data have been introduced, and in consequence the ques tion has become more complicated. The inquiry has been mooted as to whether it be advisable to throw away as use less the collected refuse, or whether it may not be employed to some useful purpose ; and if so, whether it may not be turned to account as a profitable article of commerce. Many subjects have been named, in the manipulation of which, such matters might be advantageously employed ; but of all these, the most important, and that which has the highest claim to consideration, seems to be their application to agricultural purposes, in the shape of manure. Whether indeed the refuse
of towns is of value for this purpose, has been, and still is a matter of dispute amongst persons well qualified to judge ; but we think the evidence in favour of such application 'de cidedly preponderates.
The value of manures as promoters of vegetation, is said to result from their possession of the essential element, nitro gen, in the form of ammonia, with the subordinate properties of alkalies, phosphates, and sulphates, and we learn from the experiments of Liebig, that the quantity of nitrogen contained in the excrements of a man during one year, is 16.41 lbs., and also that this quantity is sufficient for the supply of 800 lbs. of wheat, rye, or oats, or of 900 lbs. of barley. "This is much more," says the same authority, " than it is necessary to add to an acre of land, in order to obtain, with the assistance of the nitrogen absorbed from the atmosphere, the richest crops every year. By adopting a system of rotation of crops, every town and farm might thus supply itself with the manure, which, besides containing the most nitrogen, contains also the most phosphates. By using at the same time bones and the lixiviated ashes of wood, animal excrements might be com pletely dispensed with on many kinds of soil. When human excrements are treated in a proper. manner, so as to remove the moisture without permitting the escape of ammonia, they may be put into such a form as will allow them to be trans ported even to great distances." Of the success of sewage matters applied as manure, we have favourable evidence in the practice adopted at Edinburgh, where the pasture-land has been made to produce crops very considerably above the average by this means. Experiments of an equally favour able description have also been tried in various parts of this country, as well as on the Continent ; at Milan, and various parts of France and Germany. These, however, only speak as to the success of such manure in a liquid form, against which one or two practical objections may be urged. The first is the expense of distribution ; for, in the first place, the sewage waters must be raised to a considerable elevation by artificial means, for the purpose of conveying them on to the surface of the surrounding districts, and elevation will be greater or less according to the level of the neigh bourhood. The second objection consists in the limited area to which such a manure could be advantageously applied ; for if the distance were great, the necessary outlay for convey ance would form an effectual obstacle to its employment. Of a similar nature to the last, is the objection which arises from the uncertainty of the demand ; for in wet seasons, the manure in this condition cannot be applied ; and if at any time the soil be supersaturated, the vegetation is supposed to be injured thereby. Besides, if the sewage be allowed to re main on the surffice, it will emit very offensive and injurious odours, and become not only detrimental to the land, but highly dangerous to the public health.