regulate the gradual pressure. The annealing, if required, is effected in tubes of fireclay heated externally.

As metals sometimes become jagged through rolling, strips 7 millims. wide are cut out of the middle of the samples after they have been rolled to nearly the required thickness, after which the rolling is continued until they have the standard weight.

The apparatus for bending the test-strips, which is termed a "metallometer," contains two essential points, one or more vices a

for fixing the test-strips, m, and a guide, b, through which the strips pass. The guide is capable of oscillating upon two axles, c, c, which rest in bearings fixed to the vice. The weights, d, d, which are connected with the guide by means of rods, r, r, always keep the guide in a vertical position when an oscillating motion to the right or left is imparted to the vice. Thus the guide forms an angle with the vice at each to-and-fro movement, and the test-strips, which are passed through the guide and fixed by the vices, are also bent alternatively to the right and left, by preference to an angle of 67 degrees to the vertical line, until they break, whereupon the parts severed are caused to fall off by means of the small weights (g,g) attached to them. The motive power (by preference clock-work) which actuates the metallometer has a dial-plate with pointer which marks the number of to-andfro movements which the sample withstood before breaking off.

As no metal or alloy is quite homogeneous, it is necessary to make a series of tests in order to arrive at an average result.

The metallometer which was exhibited had five vices, each for two test-strips. Its working was illustrated by testing copper. The test-mark (or figure indicated on the dial of the clock-work) of a sample of commercial copper, which had been tested previously, was stated to be 51. A corre

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sponding sample of the same copper, which was tested in the presence of the Meeting, gave on the average 52.5, showing that the same quality is indicated by the same, or at least closely the same, test-mark.

Next, a sample of the same copper as above, which, however, had been heated a short time in a current of hydrogen, was tested. It is evident that the latter treatment must impair the toughness. The test-mark obtained in this experiment, being only about of that obtained in the former, proved how extremely sensitive the metallometric indications are.

Other samples of brass, steel, iron, tin, zinc, and lead, which had been prepared, could not be tested for want of time.

On Bowater's Patent for Manufacturing Railway-axles.
By ALFRED BOWATER.

A machine for manufacturing iron or steel bars at one operation into axles. These axles will be of a superior quality, more uniform in size, and cheaper and more quickly produced than those generally in use.

Under the present system of manufacturing axles, a bar or billet of iron or steel is first heated at one end and then shaped under the forge-hammer, and afterwards similarly heated and shaped at the other end, an operation of some time.

Under the above patent a bar or billet of the desired length and quality, made a little larger in diameter than the thickest portion of the finished axle, is heated

bodily, and placed in the machine, which reduces it at one operation to the required size and shape. The rolls of the machine are geared together so as to rotate in the same direction; the iron is placed between the working rolls, which are brought to bear upon the bar by powerful screws gradually pressing the rolls nearer together and reducing the bar to the required dimensions. The part of the rolls which form the tournals press upon the bar, reducing its diameter at that point, afterward bearing upon the middle of the bar, and by degrees along its whole length. As the bar becomes reduced in diameter it becomes extended in length 14 to 18 inches; to allow for this elongation, those parts of the rolls which form the tournals are arranged to slide laterally with the axle, while the rolls are screwed closer together until the finished axle is produced, and which, by the greater uniformity of the rolling pressure, gives the direction to the fibre best calculated to increase the strength of the axle.

Hydraulic Machinery for Steering, Stopping, and Working Heavy Steamengines discharging Cargo. By ANDREW BETTS BROWN.

The chief feature of novelty in the invention, as set forth in this paper, is in an apparatus called a "steam-accumulator," by which a reservoir of water at a pressure of 1000 lbs. per square inch and upwards is obtained on board ship. Having this pressure, a steering-gear of light construction and great power is made use of possessing certain relief valves, or other expedients by which perfect elasticity in the rudder may be obtained.

In a similar manner, by the use of hydraulic cylinders and rams, the same pumping-machinery and "steam-accumulator" which works the rudder at sea is made available in port for the discharge of a ship's cargo, as well as, on entering a port, to start, stop, and reverse heavy marine engines.

On Appliances for the production of Heavy Forging.
By Lieut.-Colonel CLAY.

On the Purification of Public Thoroughfares. By W. J. COOPER.
[For an abstract of this paper see Section B, page 53.]

On the Efficiency of Furnaces and Mechanical Firing.
By GEORGE F. DEACON, C.E.

In opening this subject, the author referred to one of the very numerous experiments of the late Mr. C. Wye Williams, in which air was admitted to the volatile products of combustion of the carbon through holes in an arched plate, dividing the fuel from end to end of the furnace. Mr. Williams firmly believed that such a system was capable of producing perfect combustion, and he strenuously opposed the idea that any advantage was to be gained by making use of air for the combustion of the inflammable gases which had been raised in temperature by heat abstracted from the furnace in which they were produced. The well-known experiments of Professor Tyndall and Dr. Frankland, by which it was clearly shown that, owing to the greater inability of the atoms of rarefied air, the energy of combustion was within wide limits independent of the density of the air, went far to overturn the arguments with which Mr. Williams upheld his opinions.

Arrangements similar in form to the perforated arched plate had been tried by the author; but in a series of careful experiments on a large scale only those which had included means for heating the inflowing air had been found efficient in producing perfect combustion of the gases. Transverse arched bars 7 or 8 inches high, presenting to the rising air extensive heating-surfaces, had been substituted for the bent plate, the heat for raising the temperature of the air having been ob→ tained, both by radiation and conduction, from the incandescent fuel.

The results of the author's experiments may be summed up as follows:

1st. The admission of cold air above the fuel in quantities sufficient for the complete combustion of the inflammable gases is in most cases attended with loss of efficiency, even if such admission takes place in jets over the whole surface of the fuel. Smoke, however, is considerably reduced."

2nd. By the motion of the air over heated surfaces, and its consequent rarefaction and increase of velocity when issuing from orifices in the arched bars, much more perfect chemical union with the inflammable gases is insured; the flame is rendered less luminous, but its temperature is increased; the radiation of heat is diminished, and the furnace door becomes less hot. Smoke is almost entirely prevented, and a higher rate of efficiency is attained.

The author then proceeded to explain the great difficulties in the way of working furnaces economically by hand firing, and stated that Stanley's patent machine for supplying coal to furnaces by means of horizontal fans, well known twenty or thirty years ago, but now limited in its application to a few manufactories in Yorkshire, was probably the first apparatus for mechanical firing ever made. It was difficult to understand why this machine, which with all its imperfections had been used in almost every mill in Lancashire until the new system of boilers was introduced, should be found in Leeds still at work in the crude form in which the original inventor had left it. This being the only feeder which rained down the fuel evenly on every part of the furnace, involved a principle which was clearly correct; but to render it efficient it required provision to be made for the combustion of the gases thus uniformly set free. Such desideratum the author stated had been supplied by combining with it the central arched bars. This arrangement, and the improvements made upon the machine itself, had given the following satisfactory results. The entire apparatus, consisting of a self-feeding furnace emitting no smoke, comprised considerably fewer working parts than any of the old machines. It had now assumed a form capable of being manufactured at less than one-half the cost of those mechanical stokers in which the fuel had a progressive motion towards the back, and the imperfections of which were principally attributable to the difficulty of regulating the admission of air through the bars at the back of the furnace.

The efficiency of the combined apparatus above that of the arched bar furnace when fired by hand had been found by careful evaporative trials to be 9-696 per cent. In conclusion the author stated that a feeder and furnace constructed on the principles advocated had been in successful operation day and night for nearly five months at the works of Messrs. Earles and King in Liverpool.

Some Remarks on the extent to which existing Works and Practice militate against the Profitable Utilization of Sewage. By JOHN BAILEY DENTON, M. Inst. C.E., F.G.S.

This paper points out that although the sewers of towns were not designedly made leaky, they were not constructed of a material and in a manner to secure their being water-tight, while in many cases the subsoil-water was intentionally admitted. The original "General Board of Health" recommended that all sewers should be water-tight, and that there should be a separate system of pervious channels for the removal of subsoil-water, which, it was stated, could be readily made to discharge their contents into the sewers when required for flushing or dilution. The consideration of these very important points is of little avail in those numerous towns where a complete system of sewerage works have been carried out, as the difficulty and expense of altering them would negative any such proposition; but it will be of great value in influencing the character of works yet to be performed in small towns and villages where no systematic provision exists, and in places where au alteration of existing sewers is practicable at a moderate

cost.

To show to what extent existing leaky sewers, admitting subsoil-water, will allow of the passage of sewage out of them into the surrounding soil is most diflicult; but the fact must commend itself to all, that, under certain conditions, a

fluid existing inside a sewer may pass as rapidly out of it into the surrounding ground as the subsoil-water may pass from that ground into the sewer. This effect will be conceded when the height and pressure of the one exceeds the height and pressure of the other. Though the difficulty of ascertaining the quantity of sewage which escapes is great, and the facts will only become apparent when disease becomes localized in the neighbourhood of leaky sewers, there exists no difficulty in determining the extent to which the influx of subsoil-water takes place. The greatest increase from the infiltration of subsoil-water known to the writer is at Tring and Hertford. In the first case, although the sewers are only connected with 30 houses, and the whole influx of sewage does not amount to 1000 galls. per diem, the dry-weather discharge from the main sewer amounts to upwards of 1,000,000 galls. per diem. The effect of this abstraction of water from the subsoil has been to lower all the springs in the neighbourhood, and to lay nearly dry the head of the silk-mill in the town, from whence the Grand Junction Canal Company obtained a supply of water at a summit level. In the case of Hertford, the discharge from the sewers is more than nine times the water-supply. At Blackpool, for instance, with a standing population of 7000, the water-supply is about a quarter of a million gallons daily, and the discharge from the sewers about 1,000,000 gallons. There is, therefore, an infiltration of water from some source of three-quarters of a million gallons, and no effort is made to keep the sewage on the flow when the tides rise above the sewers. In the town of Dover, with a standing population of about 25,000, where the water-supply is upwards of 1,000,000 galls. daily, the ordinary dry-weather discharge from the sewers amounts to nearly 3,500,000. Here, in order to keep the sewage on the flow," pumping is resorted to for two hours before and two hours after each high tide; and it is possible that by such means the escape of sewage is in some measure reduced by avoiding the extreme pressure of maximum accumulation. Under any circumstances it will be observed that the expense of pumping is increased by the influx of subterranean water in the proportion of 1 to 33, and, as a natural consequence, that £350 is spent when about £100 would suffice if the sewage alone was dealt with. If the returns of mortality in these places could be brought to bear, it would doubtless be found that certain epidemics are localized in the low parts of the town, while other diseases prevail in the higher parts, caused by the pent-up gases generated by detention finding their way upwards. This periodical condition of surcharged sewers is not confined to seaboard towns. In cases where the sewage is lifted, the sewer authorities may allow the sewage to accumulate in the sewers in order to avoid the expense of pumping at night, when precisely the same effect is produced as in seaboard towns under tidal influence. In many of the Lancashire towns, such as Bolton, Liverpool, Oldham, and Warrington, the aggregate daily excess due to subsoil-water in these four towns alone reaches, I have reason to believe, something between 20 and 25 millions of gallons, which, if lifted 100 feet, would cost, at 20s. per million gallons, upwards of £8000 a year. At Cardiff, in South Wales, the increase is 1,500,000, without any advantage in the way of flushing and cleansing (which, it has been stated, always accompanies the influx of water), for there the inflowing subsoil-water brings in with it a share of the sand, which deposits itself in the sewers, and is likely to become an increasing source of impediment and difficulty. In many instances of both seaboard and inland towns the sewage has been more than doubled; and wherever it becomes necessary, on the ground of health and economy, to lift the sewage by mechanical power (as we may safely assume will be the case in all towns, without exception, where the sewers have not a free flow), the difficulty and cost of dealing with such an increased quantity will become proportionately greater. These observations are made with a full recognition of the difficulty, almost amounting to an impossibility, of making ordinary sewers completely water-tight, and of the truth that water finding its way into sewers sometimes acts beneficially in flushing them, and that at certain seasons the dilution of sewage applied to irrigation is advantageous. It is to the evil of indiscriminately admitting a largely disproportionate quantity of water, without any power to regulate the time and extent of dilution, to which attention should be called with a view to determine future proceedings.

Turning from sewage works to the utilization of sewage by irrigation, which the Rivers Pollution Commissioners have recommended as the only plan of dealing with the sewage difficulty at present known, a very strong opinion has prevailed, and has been acted upon up to the present time, that it is only necessary to run the sewage over a surface of land covered with growing vegetation to extract from it all that is fertilizing, and to render the effluent liquid perfectly harmless. It has not been considered necessary that sewage should pass through, as well as over, the soil. The Rivers Pollution Commissioners themselves appear to have considered filtration, both downward and upward, separately from irrigation, and to have reported upon each as distinct operations; for, after advising a trial of intermittent downward filtration on a large scale, they add that in all practicable cases they would strongly recommend "the adoption of irrigation in preference to filtration," evidently considering that irrigation can be properly adopted without filtration. It is to this very important recommendation, as one likely to mislead if not at once set right, that attention is called; for by those who have made agricul ture a study, and have traced the effects of irrigation in England, Lombardy, and elsewhere, it is considered that no irrigation is perfect unless it be accompanied by filtration, and that if purification of the sewage is to accompany its profitable application to land, it is absolutely necessary that no liquid whatever should pass off the surface, but that the whole should go through the soil as well as over it. In no case where the sewage has uniformly filtered through a sufficient depth of soil has failure occurred. In one case (Walton Convalescent Hospital) within my own practice, the effluent water from a small area of land receiving the sewage of upwards of 300 people, having been subjected last year to a properly devised mode of natural filtration, in conjunction with irrigation, was analyzed by Dr. Odling, and declared to be "unexceptionable potable water." In this case the soil is free and porous, though it was excessively wet before it was drained. The sewage having satisfied the growing vegetation is absorbed by the soil, and passing downwards by filtration (naturally incident to under-drainage) is mixed with a constant and copious flow of subsoil-water, the level of which is maintained by the under drains. At Briton's Farm, near Romford, Mr. William Hope, V.C., has dealt with a somewhat different description of land, though of similar porosity. He has had the whole drained at a minimum depth of 5 feet, and the effluent water from the under drains, though not equal in purity to that just referred to, shows very distinctly the superiority of irrigation in connexion with filtration over irrigation simply. At Briton's (as at Walton) not a drop of water passes off the land. Though the instances are few in which irrigation and natural filtration have been associated in executed works of sewage utilization, they are sufficient to support the conclusion that no irrigation should be adopted in which filtration does not form a part of the system. At Penrith, Carlisle, and Bedford, the whole of the sewage is absorbed at the surface and discharged in different ways from the subsoil, and the amount of nitrogen and ammonia existing in the effluent water is stated, in the report of the Rivers Pollution Commission, to be as follows:

In the first two cases there appears to be no nitrogen as nitrates and nitrites, but in the last they are represented as 505. With complete pulverization of soil sewage farms may be established with security in any part of the country, inasmuch as natural downward filtration, which is only another term for subsoil-drainage, is not only a sure means of purifying liquid sewage, as shown by the Rivers Pollution Commissioners, but it is equally sure to free the atmosphere of those noxious gases which several high medical authorities have feared may be evolved from the surfaces irrigated with sewage matter.