3. Surface Channels.-For the purpose of distributing sewage by means of open carriers, or surface channels, it may, if desirable, be brought to the head of every field in a covered channel, or it may be permitted to flow through open ditches, as may be most convenient. This system, which is the simplest and most effectual, may be carried out in various ways, according to the configuration of the land. By it sewage can be at all times applied to the plant, as it merely runs in a thin film over the surface of the ground at its root; but in all cases it is necessary that the land be specially prepared for the sewage by careful levelling, and otherwise according to its natural contour. This may be done in three ways, which are respectively known as the pane and gutter system, the catchwork system, and the bed system. The pane and gutter system is the best, and is admissible in all fields having a gentle rate of inclination. The land under this system is laid out, transversely between the open carriers that distribute the sewage, quite level; the sewage is brought to the head of the field in an open or covered main carrier running transversely across it, or in the direction of its least fall; the carriers for distributing the sewage branch out from the main carriers and run down the field in the direction of its greatest fall; the sewage is distributed over the intervening space between the distributing carriers by means of stops or sluices (see Fig. 1) being placed in the carriers, which dam back the

carriers at A (Fig. 2), which being dammed up at certain points are caused to overflow, the surplus water being carried away by the

discharging drains B. A fair slope for this plan is from 1 in 100 to 1 in 120, or thereabouts.

The catchwork system is suitable in all cases where the ground has a rapid rate of inclination, as, for instance, on the side of a hill. It consists of a series of carriers one above another, as illustrated in Fig. 3. The sewage, flowing into the first and highest carrier, falls over the intervening land between it and the next lower carrier, which then takes up the water to distribute it in the same way on the land below it, and so in turn the process goes on till the bottom of the field is reached.

A

B

FIG. 3.

C

Catchwork.

The sewage is first received at A, and flows over the ground to B, thence to c, and it is finally conveyed away by the trough or carrier D. The carriers in this case may be cut at a distance from each other of from 35 to 40 feet. As to the slope itself, 1 in 12 would be found a good limit, although 1 in 4 or 5 has not been considered too steep.

The bed system is well adapted for level lands, or where there is but a slight fall. On this plan the land is laid out in a series of ridges and furrows; the sewage is admitted into carriers which run along the summit of each ridge, and falls over the incline into the furrow below. This will be readily understood from the annexed plan and description, Fig. 4.

A represents the ridge carriers which receive the sewage from the main carriers, running at right angles to them at the head of

the field, and в shows the carriers in the furrows which are connected with the discharging drains. The sides of the slopes are carefully levelled to an inclination of about 1 in 120, and the ridges may be placed at an average distance of from 30 to 80 feet apart, according to the crop put into the ground.

4. Total Submersion.-The method of carrying out this system is by raising a bank round the field to be irrigated, and then turning the water into it, where it is left until absorbed or evaporated, being from time to time replenished as may be necessary. It is extensively carried out in Piedmont and Lombardy in the cultivation of rice, and, unlike any other, it is the only system of irrigation that is considered likely to affect the health of the inhabitants in the immediate neighbourhood of its operation, its special drawback being that it converts every field where it is practised into a swamp of the worst possible description.

In conclusion, we may give the following short particulars regarding the selection of crops to be cultivated by sewage; on this point, however, more experience is required, as, owing to the greater facility by which it can be applied to grass, but few experiments have been made for its use with other crops. Fast growing, succulent grasses appear to be the favourite crops, and especially Italian rye-grass, of which crops varying from 30 to 50 tons to the acre may be obtained annually; and on one occasion as much as 61 tons were obtained in the year at the Lodge Farm, Barking. At Rugby some experiments have been made in the growth of oats, and the results reported to be of a most satisfactory nature. At Barking a couple of roods of land were ploughed up, irrigated with sewage, and sown with wheat; whilst a similar quantity of land, not irrigated, was also sown. The yield of the sewaged land was exactly 11⁄2 time that of the land which was not so treated. Mangold wurzel has been grown with excellent results at Chelmsford, and at Barking the average return has been 50 tons per acre, just double that grown upon unsewaged soil. Winter greens, lucerne, beet, flax, celery, and cabbages have all been grown upon the farm at Barking, and have produced returns beyond all expectation, the onion being the only plant that evinced any repugnance at being treated with sewage.

Experience has now shown us that town sewage is not a refuse, and that allowing it to fall into the nearest rivers, or into the sea, is nothing more nor less than wilful waste, to such an extent as to amount to a national loss, to say nothing of the consequent diminution of food which ensues by the destruction of fish. Few towns are so situated as not to be able to dispose of a portion, at least, if not the whole of their sewage upon adjoining lands, and where this is the case no more economical plan for getting rid of it has yet been devised. Where such accommodation is wanting .it may be found necessary to have recourse to some one or other of the artificial means of deodorization to which we have already referred; for although attempts to extract, by this means, a really valuable solid manure have hitherto proved unsuccessful, it would be unreasonable to draw the conclusion that means will not, sooner

or later, be discovered whereby all the fertilizing properties of town sewage may be separated from the water, and made available for disposal in the shape of solid manure.

The following is a list of the works referred to in the foregoing article:

1. Reports of the Commission appointed to inquire into the best mode of distributing the Sewage of Towns, and applying it to beneficial and profitable uses, dated March, 1858, August, 1861, and March, 1865. Printed by Parliament.

2. Reports of the Commissioners appointed to inquire into the best means of preventing the Pollution of Rivers, dated March, 1866, May and August, 1867. Printed by Parliament.

3. Lectures on Drainage, Sewage Irrigation, Water-supply, and Water-works, delivered at the Royal Engineer Establishment, Chatham, during the Autumn Session of 1867. By Baldwin Latham, C.E.

4. The Sewage Question. By Frederick Charles Krepp. London: Longmans, Green, & Co., 1867.

5. The Purification and Utilization of Sewage. By Baldwin Latham, C.E. London: E. and F. N. Spon, 48, Charing Cross, 1867.

6. Sewage, and its general Application to Grass, Cereal, and Root Crops. By Thomas Cargill, C.E., &c. Robertson, Brooman, and Co., 166, Fleet Street, London, 1869.

7. A Short Account of the Modes of Sewage Disposal in some of the Chief Towns in England. By Capt. T. F. Dowden, R.E.,

1869.

8. Report on the Treatment and Utilization of Sewage by Commission appointed by the British Association, 1869.

III. THE TOTAL SOLAR ECLIPSE OF AUGUST LAST. By WILLIAM CROOKES, F.R.S., &c.

THE important observations which were made last year with the spectroscope, polariscope, and photographic camera caused the total solar eclipse which took place on the 7th of August, and was visible over the greater part of North America, to be regarded with more than ordinary interest, as it was anticipated that the few minutes' opportunity then afforded would enable several points left doubtful last year to be satisfactorily cleared up.