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from the end of the lever. H a second lever employed to control

H the first, 2 ft. long, and turning on a fulcrum 5 inches from the centre of the suspended weights; I hand-rod hanging from the lever H, by which the entire system of levers was moved. N(fig. 2) is the piece of wood with the nail in it (not seen in the figure) by which the levers were prevented from acting, and the explosion produced.

Neither the exact amount of the weights suspended from the first lever, nor the weights of the valve and levers themselves, appear on the face of the proceedings; and without these it is impossible to calculate the actual pressure to which the boiler was subjected. This is of no great consequence however; for, as suggested by Mr. Barnes and Mr. Farey, in their evidence, this is not a case where the question turns on the particular amount of pressure exerted, but where the stoppage of the valve set all calculations of resistance at defiance.

There were five persons killed by the accident; and there have been two Inquests, of the proceedings of which the following is an abstract, stripped of everything which has not some material bearing on the case.

Evidence bifore the Coroner.- Mr. Frederick Braithwaite, engiweer, examined.--The boiler was what is termed a tubular boiler, the dimensions of which are stated in the plans given in. It was intend ed to drive one of a pair of 25-horses low-pressure engines on board the Waterman steamer, No. 11. It had been applied to that purpose. It could uot make sufficient steam, and was taken out after it had been used some ten or twelve times. It was too small as regards the steam required to be created for that purpose. Had seen the boiler for sev- . eral months standing on Fairbairn's premises, but had lost sight of it for months till he saw it after the accident. Did not know when Samuda bought it. The boiler was made about 18 months back--certainly within two years.

John G. Burnard examined. - Is a millwright and engineer, and was in the employ of Messrs. Samuda.-1 cannot say there was more than 20 lbs., but I believe so. I did not weigh the valve. The handle of the safely-valve was propped up so as to prevent its acting.--There were two weights, one round, the other square; that on the safety-valve was square, (a plan was here put in illustrating the Witness's meaning. See fig. 3.) I saw the piece of wood placed against the boiler to keep the lever of the safety-valve up. Lowe told me to get a hammer and a nail. I could not get a hammer, so brought a chisel, and drove the nail with it. Lowe held the handle of the lever of the safety-valve whilst witness drove the nail into the wood. In doing so, Lowe pulled the handle down, upon which the steam blew oti' strongly. After the nail was driven, the piece of wood was placed under the handle of the valve, thereby supporting it, and preventing its action. I saw Lowe place the wood against the boiler, after which the nail was applied. The handle of the lever of the safety-valve, before the wood was brought, rested on a rivet in the boiler. The nail would not bear so much pressure as the rivet, although it would have the same effect, I renoved the lever off the rivet several times, because I thought it dangerous, and that no one in their senses would do as Lowe had done, as it prevented the use of the safety-valve al


together. When he left the boiler, the handle of the safety-valve rested on the nail. The explosion took place ten minutes or a quarter of an hour aster. There was only one safety-valve. There was no steam-gauge on the boiler, but there was a water-gauge, which was broken. There were two gauge-cocks, but they were not put on in the proper place. The upper one blew off steam instead of water.

Mr. John Farey, C. E., examined.—Had seen the boiler since it had been removed from the spot where it stood at the moment of the explosion. The boiler had burst the exterior shell out wards; it had noi collapsed. The boiler has been burst by a very intense pressure, which is not accountable for by any supposition of the safety-valve seen by witness being merely overloaded, but that it must have been fastened down, which circumstance rendered this case very distinct from most of the explosions on record. All the steam which was produced being retained and accumulated in the boiler to a pressure which burst the metal with extreme violence, projecting large pieces to a great distance through the air. One piece in particular had cut itself into the bricks of a wall at a considerable distance from the boiler, which showed that that particular piece had been projected with a velocity to be expected from an explosion of gunpowder, but not from the ordinary explosion of overloaded steam boilers. The earth whereon the boiler stood had been forced downwards by the violence of the explosion, that being a symptom frequently found in the explosions of gunpowder, but not a usual symptom in explosions of steam boilers. These appearances convinced witness, quite independently of any information to that effect, that the safety-valve had been fastened down; and the engines not working at the time to any speed which would consume steam, all that was produced was accumulated, and having little or no escape, or expenditure, that accumulation caused the explosion. It is quite true that 100 lbs. on the square inch could not have produced the effects he had seen there. Witness was no convert to the theory of the production of gas within a steam-boiler, or that the explosion of hydrogen gas could be produced, unless in cases where the boiler was nearly empty, and the iron red hot in the vicinity of water. There were no appearances in this case of that having taken place. llad never met with one case under these conditions. No atmospheric air can get into a boiler when under pressure. The supposition that hydrogen gas may be produced within a boiler is, that a portion of water has had its oxygen absorbed from it by the oxidation of ihe heated metal of the boiler. If that did take place, oxide of iron must be found in the boiler in palpable quantities. There were no appearances in the present case of any oxide of iron. Another supposition is requisite to account for an explosion taking place from the hydrogen gas supposed to be produced, viz., that atmospheric air, or oxygen in a gaseous state from some other source, should become mixed with the hydrogen, for it is only the mixture of hydrogen and oxygen, in their gaseous states, which is susceptible of explosion. The explosion being, in fact, a combination of the two gases, previously mixed in suitable proportions for combining, and by their combination at the moment of explosion, or ignition, they produce water. The supposition is that water is first decomposed, and afterwards recomposed. In the present case there were no symptoms of such having been the case, or of any oxidation. There were no appearances of deficiency of water in the boiler. The uppermost row of tubes, which must have been the first to have been laid dry by deficiency of water, were of brass, and show no symptoms of having been overheated; and if they had been overheated, brass would not absorb oxygen from water in sufficient quantities to have liberated any hydrogen. The tubes lower down were iron, and presented no appearance of having been red hot. No one can mistake iron that has been red hot. Has had many years' experience of explosions in gas works,--they were occasioned by a mixture of hydrogen gas and common air. Such explosions are always attended with fire and burning. Was acquainted with attempts some years ago to construct engines to be impelled by means of a vacuum and such explosive actions as substitutes for steam-engines. The symptoms attending such explosions are so distinct from anything belonging to this case, as to leave no doubt whatever on witness's mind, that the accident was not occasioned by ignition of gas, but by steam alone, confined and retained to an excessive pressure. There are two cases on record of similar explosion from safely-valves being fastened down. One of the earliest was a case of a boiler of one of the earliest attempts at locomotive engines; the other was at Lyons, where Mr. Steel lost his life. Except from gunpowder, never saw such an explosion as the present in its effects.

The Corouer, in summing up, observed that in his opinion, the evidence showed, most distinctly, there had been an undue pressure of steam upon the boiler; and he could not but lament that the remarks which fell from him upon the occasion of the inquest on the parties killed by the explosion on board the Gipsy Queen had not had more etiect in inducing a proper degree of caution.

The jury retired for half an hour; and on returning into court,

The Foreman stated that it was the unanimous opinion of himself and brother jurors that George Lowe was guilty of manslaughter.” The foreman said he was further instructed by the jury to express their opinion “That the machinery employed on Mr. Samuda's premises was altogether of an inefficient character.”

The Coroner said he quite agreed with the verdict of the jury; and he hoped that the caution with which they had accompanied it would have a proper effect on Mr. Samuda.

On the Condition and Ventilation of the Coal Mine Goaf. By

Prof. FARADAY. None of our readers can have forgotten the terrible loss of human life which occurred at the Haswell Colliery, in the county of Durham, last September. Ninety-five persons perished in an explosion within that mine. Professors Lyell and Faraday were inmediately sent by the Secretary of State to attend the judicial investigation which was held in consequence of the accident, and to inquire into its cause.These gentlemen have since made a Report to the proper authorities, which is now before the public; and the object of Prof. Faraday's communication was, to illustrate by experiment what he had represented in that document. The arrangement adopted by the Professor invited attention, 1. To those parts of the mine in which the explosion occurred. 2ndly, to the circumstances of the calamity. 3rdly, to the means of preventing the recurrence of a similar accident. 1. With respect to the locality of the explosion. It appears to have occurred at a spot in the mine which Professor Faraday described with great accuracy: this is called the gonf. In working a mine, low,narrow passages, at right angles with each other, are cut through the seams of coal. The square masses made by these passages are called pillars. These pillars are gradually cut a way, and replaced for a while by systems of wooden props; and the place where these props replacea pillar is called a jud. in time the jud is removed, and then the insupported roof of the mine falls in. The heap of runs thus occasioned by the successive drawing of contiguous juds is called by miners a goaf. When the mine is deep, and has been long worked, the size and height of the goaf are enormous: one of the goals at Ilaswell extends over thirteen acres, and the height of it cannot be ascertained. Corresponding with this heap of rocky fragments, and produced by it, is a cavity in the mine like an inverted basin, including a thin belt of air which surrounds, and partly perineates, the goat. It is this aërial space which Professor Faraday regards as a magazine of danger.-The air itself is, or may be, the fire-damp (the light hydro-carbon gas) and common air, mixed in very various proportious. The lightness of this gas, and therefore of the mixture, causes it, if present, to ascend into the upper part of the goaf cavity, which is then converted into a reservoir of explosive matter. Prot. Faraday, secondly, described the probable circumstances of the accident as it happened.-Some disturbance of the goaf-cavity, occasioned by the drawing of a jud, and possibly a change of the pressure of the atmosphere, diffused the fire-damps through the workings at that place. This, when lighted, would, by the explosion, raise, and then kindle, the coal-dust which is always abundantly pervading the passages; and these effects must, in a moment, have made the part of the mine, which was the scene of the calamity, to glow like a furnace. This conflagration was necessarily succeeded by vast volumes of the poisonous choke-damp (carbonic acid gas,) so that it was humanly impossible for any one within the range of the explosion to have escaped alive. Prof. Faraday then entered, thirdly, on the most important part of his subject, viz. the prevention of such calamities when occasioned by the gouf. Ile proposes the ventilation of the goal. He expressed his opinion, that it would not be so well to attempt this by driving the contents of the goas through any parts of the mine which are occupied by human beings; but he exhibited how the goaf-cavity might be exhausted of noxious air by means of a pipe rising as high as possible-from four to eight or ten feet-into it, and communicating at its other extremity with the return way, or the upcast ventilation-shaft. He illustrated thie readiness with which this might be done, by most conclusive experiments. He filled a glass vessel (which represented the goaf-cari. ty) with inflammable air, smoke, &c., and then exhausted it in a few seconds, by means of a pipe communicating with the flue of one of the small furnaces in the theatre. He used tubes of thin sheet iron and of air-proof cloth for experiments on large and rapid currents, proposing (to avoid the effect of excess) to suspend them, or place ihem on props in the open space of any passage most convenient for the purpose; and said ihat such a tube, or even others made by nailing four boards together would be sullicient for the purpose. Ile showed that the terminal ends of these need not be reversed every time the upper end of the goaf changed its form, and concluded by confuting objections that had arisen in his own mind, or might be urged against the details of the arrangement he recommended, and stated his belief, that it was in reality as practicable as it was theoretically uninpeachable.

Lond. Athenæum.

Expeditious Bridge Building. Mr. Dredge has just erected a bridge over the Blackwater river, county Tyrone, Ireland. This Bridge has been in contemplation nearly forty years, the only obstacle being the immense expense of any structure on the old system, and probably for forty or a hundred years more the connty would have been deprived of the advantage now conferred, but for Mr. Dredge's estimates, and his highly-approved plan. Mr. Dredge has not added much to the long delay; by any dilatory process of construction ; when the iron was on the ground he astonished the public with the rapidity of the work, the bridge being extended and completed in one week. The bridge is 74 feet span, and for the heaviest traffic. It was erected at the cost of the Earl of Caledon.-Wiltshire Independent.

Account of the Raising of the Spire of the Church of the Nativity,

in Spring Garden, Philadelphia county. By N. LE BRUN, Architect.

Communicated for the Journal of the Franklin Institute. The Doric tower on which this spire was raised, faces the east, and is 90 feet in height, it is strengthened at the angles by four double buttresses, projecting at the base four feet; the projection of these buttresses is diminished at four stages in their height. The interior figure of the tower at the base is a square, but mid-way it assumes the figure of an octagon by gathering over the brick work at the angles; the whole forming a construction of the most solid character. The octagonal spire, which was finished complete in front of the tower previous to raising, is so feet high, including its crowning ornaments; its width at the base is 12 feet 6 inches,

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