Yet the problem, though difficult, must be solved, or our great cities will be destroyed by their own physical impurities. The growth and expansion of cities, throughout the present century, have been wholly beyond precedent; and thus the difficulty of making a satisfactory disposition of their offal has been fearfully augmented. The sewerage of our streets and houses modifies the problem, but does not solve it. Desolating epidemics, like the Plague, Yellow Fever, and the Cholera, will often visit our great cities, and decimate their people, unless means can be found to cleanse them wholly and incessantly of whatever tends to pollute and render noisome their atmosphere. SEWAGE is the term used in England to designate water which, having been slightly impregnated with the feculence and ordure of a city or village, is diffused over a farm or farms adjacent, in order to impart at once fertility and moisture to its soil. To secure an equable and thorough dissemination of Sewage, it is essential that the land to which it is applied, if not originally level or nearly so, shall be brought into such condition that the impregnated water may be applied to its entire surface, and shall thence settle into, moisten, and fertilize, each cubic inch of the soil. This involves a very considerable initial outlay; but the luxuriance of the crops unfailingly produced, under the influence of this vivifying irrigation, abundantly justifies and rewards that outlay. As yet, the application of Sewage is in its infancy; since the perfect and total conversion of all that a great city excretes into the most available food for plants, requires not only immense mains and reservoirs, with a costly network of distributing dykes or ditches, but novel appliances in engineering, and a large investment of time as well as money. Years must yet elapse before all the excretions of a great city like London or New-York can thus be transmuted into the means of fertilizing whole counties in their vicinity. But the work is already well begun, and another generation will see it all but completed. Meantime, many smaller cities, more eligibly located for the purpose, are already enriching by their Sewage the rural districts adjacent, which they had previously tended strongly to impoverish. Edinburgh, the capital of Scotland, is among them. The little village of Romford, England, is one of those which have recently been made to contribute by Sewage to this beneficent end; and a visit of inspection paid to it, on the 15th of October last, by the London Board of Works, elicited accounts of the process and its results, in the London journals, which afforded hints for and incitement to similar undertakings in this and other countries--undertakings which may be postponed, but the only question is one of time. _The Daily News_ of Oct. 17th, says: