of the sewage per ton. In giving my opinion, therefore, on these points, I do so with some diffidence, considering the eminent authorities who take contrary views. From my own observation, however, and after consideration of the whole subject, and elimination of whatever is obviously too sanguine on the one hand and too damping on the other, I have been enabled, as an engineer, to form some definite views, which may contribute towards a practical solution of the problem.

Without reference either to the value of the sewage or the quantity used per acre of land, and applying equally to every town, there are two very important points in the consideration of the utilisation of sewage, both in a commercial and an engineering point of view. One is, the area of land which can possibly be irrigated during the course of the sewer; and the other is, the outfall for the sewage at times when, either from wet weather, frost, or other reasons, the whole of it cannot be used on the land through which the conduit passes. The most perfect system attainable would be, to sell or utilise all that was possible on the way to the outfall, but to have the outfall itself on worthless barren sands belonging to the corporation or company to whom the sewage has been conceded. During the time when there is no market for the sewage in transitu, it can be used for the fertilisation and benefit of the land at the outfall. If it should be found to pay better, not to sell any on the way, then the whole can be used on the promoter's own land. But my impression is, that when the farmers find the sewage absolutely brought past their doors, and that by using it they may, without doubt, double or triple the amount of grass grown on their farms, they will be glad to buy it, and most probably will use all they can get. In this case the whole can be sold for the greater part of the year, and only used on the barren lands at the outfall, when not wanted above. It is the want of a constant and certain outfall which is one of the greatest objections to some of the schemes proposed for London, especially to the one. favoured by the corporation, of pumping the sewage to heights near the town, and then distributing it by hose.

VOL. VII.

F

and jet over the surrounding fields. What is to become of this mighty stream of filth when there is no market for it? It must fall back into the Thames, and render useless the present great expenditure for the purification of that river.

With regard to the quantity of sewage to be applied per acre, one set of authorities advocates the application of large quantities to the land; the other, of small dressings, not exceeding 500 tons, or the sewage of about ten people per annum. When we consider that this latter quantity represents a total depth in the year of only five inches over the surface, and that at Craigentinny, the depth applied must be at least eight feet, the difference between the two systems is very striking. There can be no doubt, however, that the sewage at Craigentinny, being had for nothing, is most lavishly used, and might be greatly economised with the same results to the land.

While we have no exact data at present as to the minimum quantity which may be used with advantage or profit, I think we have clear evidence as to the maximum. Upon looking over the evidence before the Special Committee, in 1864, of Mr J. B. Lawes, who has been conducting the systematic experiments at Rugby, I find he states (in answer to question 4351), that, where the unmanured land produced 9 tons of grass per acre, he obtained 22 tons of grass by using 3000 tons of sewage, 30 tons of grass by using 6000 tons of sewage, 32 tons of grass by using 9000 tons of sewage. The first 3000 tons, therefore, gave an increase of 144 per cent. on the unmanured field; the second 3000 tons gave an addition of only 36 per cent. on the total result of the first quantity; while the third 3000 tons gave only an extra 7 per cent. on the result of the second.

Here we see that by far the greatest comparative result was given by the first 3000 tons of sewage; and that, while it might be a question whether it would be worth while to pay for a second 3000 tons, it would clearly be most unprofitable to pay for a third 3000. Of course, where the sewage can be had for nothing, the full 9000 tons per acre may be applied; but, even then, it probably does more harm than good, by making the grasses too rank.

All this, I think, points to a profitable maximum of about 5000 tons per acre, or fully four feet deep of sewage during the year. Some soils will no doubt require a little more, and others a little less, according to circumstances.

On the question of value per ton, we must also accept Mr Lawes' evidence of what he would give, as a farmer, for sewage, as the best guide at present on this important point; more especially when we find that, practically, it lies between the scientific values of two eminent authorities on chemistry-Dr Hoffman and Professor Anderson. Mr Lawes says he would rather give 2d. a ton for it, if allowed to take it in such quantities, and at such times, as he liked, than d. a ton if he had to take it regularly at all times.

Now, in the case of a corporation or company having an outfall on land of their own, upon which to put the sewage when it was not wanted by the farmers on the way, the average value of the entire sewage might, I think, be fairly and safely taken at 1d. per ton. This value, while only about one-half of that assigned to sewage by Dr Hoffman and Baron Liebig, is double what Professor Anderson thinks is the extreme value, viz., d. a ton.

The plan proposed by Messrs Napier and Hope for the utilisation of the sewage of London is not altogether novel in its main features. In 1856 Mr M'Clean, the present President of the Institution of Civil Engineers, suggested a somewhat similar idea, which was supported also by Sir Morton Peto. He proposed to conduct the whole sewage of London through the county of Essex to a point on the coast between the rivers Blackwater and Crouch, using it on the way to irrigate whatever land could be reached by gravitation.

Seventy-three of the occupiers of lands in the southern division of Essex memorialised the Board of Works to adopt this project, and I am not sure but what the scheme got so far as the preparation of Parliamentary plans.

Some years after, the Board of Works advertised for plans. and tenders for the sewage; and, after some delay, the pro

posal of Messrs Napier and Hope has been accepted, and a concession granted to them on certain terms.

Several changes and modifications of the scheme have taken place during the negotiations; but I have the authority of Mr Hemans, with whom Mr Bateman has lately been associated, as to the information about to be given: I may here mention that Mr Hemans is also engineer for the utilisation of the sewage of Dublin, which it is intended to discharge upon the North Bull Sands in Dublin Bay. When we examine the contour of the county of Essex, through which the London sewage is to be taken, we find it peculiarly adapted for the purpose. There is also no county in England in which the proportion of waste land is so small; and, from being wholly agricultural, the people are found in moderate-sized, and not in large towns. The part which lies in the southern portion, on the banks of the Thames and on the sea-shore, is of moderate elevation, and is a rich alluvial soil on a subsoil of very tenacious clay. Under cultivation, this produces very abundant crops of wheat, beans, and clover; indeed, the best wheat in the London market is that from the Essex "hundreds." Most of the farms in South Essex have more or less a proportion of rich marsh land, the edges of the coast towards the Thames and sea being flat, and broken into creeks and islands, with great breadths of sands drying at low water. On these fringes of flat land oxen are fed, and hay grown for winter consumption. In some parts the scarcity of water is severely felt, and throughout the county generally there is a small rainfall, perhaps ten inches less than in more western counties of England. The great mass of land is arable at present, but meadow grasses could easily be grown, if the rain-fall were to be supplemented by a supply of sewage.

Through this favourably situated county, therefore, it is proposed to take the sewage of London on its way to the outfall on the coast; and the contour of the land is indeed so favourable, that at least 80,000 acres can be commanded by gravitation alone from the main culvert and its branches. The promoters will irrigate a few fields for themselves here and there, as advertisements to show what can be done by

sewage; and I think it cannot be doubted but that the farmers will soon find out its advantage, and be ready to give a good price for this stream of wealth flowing past their doors, more especially when we consider that it is daily becoming more difficult to grow corn in this country with profit, and that stock and dairy farms are found to be more remunerative.

The present dry-weather sewage of the north side of London, with a population of 1,800,000, is 10,000,000 cubic feet a day; but the prospective sewage may be taken at 11,495,000 cubic feet. Besides this, the Metropolitan Board of Works provides for an extra of an inch of rainfall; but the promoters only propose to take the dry-weather sewage, ten million cubic feet a day, or about 100,000,000 tons per annum, at present.

The main culvert is to tap the northern main outfall sewer of the Metropolitan Board of Works at Abbeymills, three miles from London, receiving the sewage there considerably above the level of high water. The culvert then runs for a distance of six miles, when it is joined by a branch conduit from the Barking outfall reservoir; it then passes on for a further distance of twenty-two miles, sometimes in cutting, sometimes on embankment, until it reaches the head of the navigation of the river Crouch, at Battle-Bridge in Essex, twenty-eight miles from the commencement at Abbeymills. Up to this point the sewer consists of a circular brick culvert ten feet in diameter, as much as possible half in and half out of the ground. The culvert will take 9500 cubic feet per minute, but with the present dry-weather sewage it will only have 7000 cubic feet, and only be three-quarters full. The reason for starting the main culvert at Abbeymills, and not at the Barking outfall, is to take advantage of the higher level of the sewage at the former place; the level of the bottom of the culvert at Abbeymills is six feet above Trinity high-water mark, and from thence it falls gently for more than three miles. The level of the ground then requires that the sewage be lifted up twenty feet by pumps, and between the ninth and tenth mile it has again to be pumped up for twelve feet. Previous to this last lift, however, the