could not tell where the water was. When the accident occurred the water was between the lower and the second gauge-cock. He could tell that by opening the cocks. They could never depend on the gauge-glasses, and the floats never acted. The river water fermented more than the sea water. He thought the water spaces were too narrow, the fire causing a greater ebullition. He considered the true water level which ought to be kept up in the boilers to be about 8 inches above the feed-cocks or the surface of the flue. That would be plenty of water, in his opinion.

A reference was here made to the plans left by Mr. Ewart, the government engineer, for the guidance of the jury, but they were found to be incomplete, inasmuch as the place of the gauge-cocks of the boilers had not been distinctly pointed out; it was generally understood, however, that the witness meant that the water was between the lowest and second gauge-cocks.

To a general question by the jury, the witness said he was quite sure there was plenty of water in the boilers when the accident happened. The water was between the lowest and second gauge-cock, and that was sufficient. If too much water came from it I should say the boiler was too full. The water-line, in my opinion, is below that level.

The witness here became so much exhausted that it was found necessary to adjourn to allow him time for refreshment and rest.

On the jury reassembling,

Mr. Hall asked the witness if he worked the boilers of the Victoria with water above the second gauge-cock.

The Witness.-Yes, I have with the fermented water. I never knew any real or solid body of water at all in the boilers, it always appeared in a state of ferment. I was always in bodily fear, but I thought there was no danger when there was plenty of water in the boilers. The other engineers had the same feeling. We were always examining them, every three minutes at most, and have known the water to lower from the top gauge to the second in less than five mi. nutes. I have not mesured what quantity of water the boilers could contain. I shut the feed-cocks off myself directly after the collision with the brig. The witness here pointed out the way in which the feed-cocks were situated, and the way in which they would be when turned off. He further said the chief engineer could not read the words "shut" and " open," but knew when the feed-cocks were open or shut by practice. He was in the habit, with the other engineers, of regulating the feed, and as the mid

ship boilers would be supplied in their work. ing by the wing boilers, the feed was gene. rally turned nearly off in the midship boilers whilst they were kept fully open in the wing boilers. This was the case with them when the collision took place, and he turned the feeds off. This was not a regular mode of working boilers, but these boilers required great attention, and required to be worked in this way. Furnace plates of other boilers were generally half an inch in thickness. Witness never saw any so thin as the Victoria's, which are about a quarter of an inch thick.

The coroner was about to arrange the voluminous evidence, previous to summing up, when Mr. Hall requested that James Craig, an engineer, who had the charge of the vessel on one voyage, and who was examined in the early part of the investigation, should be recalled.

Craig was accordingly sworn; and in answer to questions by Mr. L. Jacobs, he said that he knew the witness Cordinow. He was chief stoker on board the Victoria. He was not an engineer. He instructed this man to keep the boilers perfectly fed, and not only him, but every other man in the engine-room. A person of the name of Tempest, a neighbour of Cordinow's, was also on board, and was also instructed, and they all expressed their satisfaction at the working of the boilers, but said they were not up to the mode of feeding till he pointed it out. He showed them exacted how to fix the lever. He always kept the water in the second cock, and steam in the top cock. To make her quite safe, he should always keep the water between the second and third cocks. The supply pipes were sufficiently simple to regulate the feed without opening the furnace doors or any other help. The stoke-hole was large enough. He considered the chief engineer a very competent man, but he had not so good an opinion of Colvill, the second engineer. He had been chief engineer of 37 different steam-boats. He never found any difficulty in managing any engines. The engines of the Victoria were as easily worked as any others.

The coroner said he had no doubt that they might supply the water very well, but the question was whether the engines worked well afterwards. He asked if the fire drove the water out of the narrow interstices?

Craig-As engineers we have been always taught that the steam will find its way through the water, which will find its level.

At 8 o'clock the coroner proceeded to read over the whole of the evidence taken

in this case, which occupied upwards of

three hours.

The jury retired at 12 o'clock to consider

of their verdict, and at half-past one they were prepared to deliver it.

Mr. P. Mellish, the foreman, rose and said, that he was never placed in a more difficult situation than he was that night. He had to contend with difficulties he never had to contend with before. He had now to declare the opinions of the jury. He believed he spoke their feelings when he said that they never saw a steamer fitted up with greater splendour and taste than the Victoria, or with greater attention to the convenience of the passengers. He must, however, say, and he was delivering the unanimous opinion of the jury, that they never saw a vessel in the river fitted up with so little regard to the comfort of the engineers and stokers who worked the engines, and the place where they were employed; in fact, it was a perfect pandemonium, at least such was his opinion. He never saw a place which realized his ideas of pandemonium so much before.

The Jury-It is our opinion generally it is not a fit place for the engineers and stokers.

The Foreman continued-I will now deliver the verdict of the jury.-"They consider that the death of Andrew Brown [and the other sufferers] was accidentally occasioned by the explosion of the boiler on board the Victoria steam-vessel, on the 14th of June last. The jury consider that the construction of the boilers was unsafe, the water spaces too small, and the plates too thin. The jury further consider, that the engineers having no immediate control over the safety-valve in the engine-room is highly reprehensible, and the jury levy a deodand of 1,5001. upon the boiler and steam-engine of the Victoria."

NOTES AND NOTICES.

Magnetic Fluid.-During the late storm at Rochdale, a cotton-mill was struck by the lightening, and the bell which hung above the roof was destroyed. It was afterwards found that all the tools of a watchmaker residing in the neighbourhood, had become in a greater or less degree magnetic, and were wholly useless; they all attracted iron filings readily, and the hammer was polarized, the needle being neutral. -Athenæum.

London and Birmingham Railway.-On Monday last, a large party of the directors and Proprietors breakfasted at the Birmingham station, and at halfpast six they left, with one of Mr. Bury's engines, to make the first excursion along the entire line to London, where they arrived at the Euston station

at one o'clock, without any kind of accident or circumstance to interfere with the pleasure of the journey. The time occupied in travelling was exactly five hours, the other hour and a half being devoted to the examination of the stupendous and interesting works on the new part of the line, much of which is yet incomplete. The distance to Coventry (184 miles,) was performed in 36 minutes; from Coventry to Rugby (11 miles,) in 22 minutes; from Rugby to Denbigh Hall (35 miles) in 2 hours and 10 minutes; and from Denbigh Hall to London (48 miles) in 1 hour and 54 minutes-in all 5 hours and 2 minutes. The Kilsby Tunnel has been constructed in defiance of immense of physical difficulties, and is a work which has excited the greatest interest and admiration. Arriving at the central shaft which has a diameter of 60 ft. they were saluted with hearty cheers from a number of workmen who had stationed themselves at its summit far above the subterranean travellers who responded to the welcome. The rocky excavations at Blisworth, extending through a very considerable extent of country, astonished the visitors, perhaps, as much as any other part of the line, and must be seen to enable any person to form an adequate idea of its character. The Wolverton viaduct excited great admiration, and many of the proprietors walked down the embankment to enjoy a view of the beautiful structure, from the meadows below. At the great Wolverton station, or central depot for the engines, the workshops, and arrangements were inspected, and refreshments were liberally provided. The remainder of the journey, although entitled to notice, presented fewer features of novelty. The jaunt gave much satisfaction.-Midland Counties Herald.

By

Steam-Boats beaten in Speed.-Mr. Jobard, of Brussels (says the Nouvelliste), has discovered a method, according to which it is asserted that the Straits of Calais may be crossed in eleven minutes, by means of a pyrotechnical composition, of which the chlorate of potash is the basis, but in a less proportion than in Congreve rockets. The whole apparatus consists in a boat, with the floating properties of the life-boat, long and narrow, crossed at its greatest diameter by one or more iron tubes charged with the pyrotechnical composition. applying fire to these tubes, the openings to which should pass beyond the stern of the boat, the reaction is stated to be such that the boat will glide over the water with a swiftness never attained on any railway. The construction being upon the principle of the life-boat, the person embarking in it will run no other risk than that of getting a few momentary duckings, but will always rise again to the surface. The building of the boat will not cost more than about 1000 francs, and each voyage will require 100 francs' worth of gunpowder.

Flat-chambered Boilers.-We have received a letter from Mr. Hancock in reply to Mr. Hebert and A Shareholder; as we have not been able to publish it this week, it is but fair to state that he very clearly refutes Mr. Hebert's objections to the merits and originality of his invention of flat-chambered boilers, and shews that Raddatz's patent, referred to by A Shareholder is quite different from his.

The twenty-eighth volume of the Mechanics. Magazine is now published, price, in half-cloth, 8s. 6d., with a Railway Map of England and Wales. The Railway Map may be had separately, price 6d.; and on fine paper, coloured, price ls.

IMPROVED METHOD OF MINE VENTI

LATION.

SIR,-As you have always shown an anxious desire to promote the safety of the working miner, by disseminating, through the medium of your useful periodical, any information bearing on hat object, I am induced to trouble you with the particulars of a plan for assisting ventilation, which I have introduced successfully at a colliery under my management in Derbyshire, and which has been tried at two neighbouring collieries with equal effect. It is, perhaps, necessary I should first state, that the principle of ventilation is simply that of a pneumatic balance, where one scale is made to preponderate, either by receiving an increased supply of air, or by a reduction of weight in the opposite scale by rarefaction. To promote this object of rarefaction in the north, powerful furnaces are placed at the bottom of the upcast shaft, the heat from which expands, and lightens the long column of air above, and thus promotes a constant circulation. This method, though efficacious, is open to several objections, amongst which are the danger and expense of feeding the fire, and the necessity of confining the upcast shaft entirely to the purposes of ventilation, as suffocation must inevitably ensue should any one attempt to descend through the smoke and vitiated air voided therefrom. The plan I have adopted, though, perhaps, not so powerful as that used in the north, is certainly much more simple and less expensive; and the result of three years' experience has proved it to be quite sufficient in all ordinary cases for the removal of those pests to the miner, carbonic acid gas, and the more dangerous hydrogen, both of which it has had to contend with in formidable quan ities. My plan (see sketch) is as follows:

At a distance of 4 feet from the side of the upcast shaft A, (which is here used for drawing coals,) I sink a small shaft B, 4 feet diameter, and 14 yards deep, the top of which is closely covered with a pair of folding iron doors C. At 2 feet from the bottom of this shaft an opening D is made into the upcast shaft 2 feet 6 inches high, and 2 feet 6 inches wide, the sides of which are secured with brick walls, and the top supported with broken cast rails. At 2 yards from

the top of this hole another opening E of the same dimensions cominunicates with the main shaft, and is secured in a similar manner. A fire-lamp, F, 2 feet 6 inches high, and 18 inches wide is then filled with fire and lowered into the small pit to the space between the holes D and E; the doors are now closed, when the heat and smoke, with a portion of rarefied air, rushes through the top hole E, and mixing with the air in the upcast shaft, so lightens it as to produce a very strong and continuous current through the mine to the surface. A few weeks ago I effected a considerable improvement by suspending to the chain in the small shaft, at a little distance above the uppermost hole E, an iron cover G, which nearly fills the shaft, and thus preventing the escape of any portion of the heated air or smoke through the folding doors above, renders the whole available for the purpose of rarefying the air in the upcast shaft A. In practice I find the depth I have chosen for the small shaft B (14 yards), to be the most convenient, as one man can with ease wind up the fire and repair it, and there is no inconvenience to the workmen in descending for this distance through the smoke. I am, Sir,

Your very humble servant, THE BLACK DIAMOND. Kilburne, near Derby, July 27, 1838.

The strength of a cylindrical tube to resist an external pressure exerted on its outward surface, is a very different thing from the strength of the same tube to resist an internal pressure.

In the latter case, that is, when the force is exerted on the inside of the tube, and tending to burst or rend it asunder, the relative strength or power of resistance of the tube is very easily estimated, it is well known to be, under like circumstances, in the simple ratio of the thickness of the metal of which the tube is formed, and inversely as the diameter of the tube.

But in the other case, when the pressure is external, the strength of the tube to resist such pressure will depend upon very different principles :-it is generally supposed that the strength of a cylindrical tube under such circumstances must be immeasurably great; and there is no doubt that such is really the fact, provided the pressure is uniform all round the tube, and that the true cylindrical figure is strictly preserved; because in such case the tube is like a well-formed arch; it cannot be destroyed except by the absolute crushing of the particles of metal one into the other, which is altogether improbable. But if the true cylindrical or circular figure is not preserved, and indeed if the deviation from the true figure of greatest resistance is ever so trifling, the principle of the arch is gone at once, it is then like an arch without abutments; and the tube under such circumstances,instead of being able to resist almost infinite pressure, will in fact be unable to resist a comparatively moderate pressure.

Now, practically speaking, it is almost impossible to form a tube that shall be

*As a strong corroboration of this fact it may be stated that about fifteen years back some interesting

strictly cylindrical, or of any other figure of greatest resistance; the very weight of the material is sufficient of itself to destroy the true figure; the circumstance of the tubes of steam boilers being formed of metal plates with lap joints rivetted together precludes the possibility of obtaining the true figure; moreover, in the case of horizontal tubes, as they are employed in steam boilers, the pressure is not uniform; for while the pressure on the upper part of a tube six feet diameter may be only 13 lbs. upon the square inch, the pressure on the lower part of the tube will be nearly 164 lbs. to the square inch, because the weight of a colunin of water six feet high has to be added to the pressure on the lower part of the tube; therefore the cylindrical or circular form is not in that case the true figure of greatest resistance; and it is not very likely that in the ordinary way of business, of boiler making, much care or correctness can or will be bestowed to the calculating, or afterwards in the making of the tube, agreeable to the true figure of greatest resistance.

Moreover, if all the above difficulties be overcome, and the tube is formed according to the true figure of greatest resistance, there is little chance that it will long remain so, in the practical working of a boiler; the unequal contraction and expansion of the plates by being partially overheated and then suddenly cooled, accidents of constant occurrence, will cause the plates to be drawn and buckled, and thereby soon destroy the true figure. And it should be borne in mind that however trifling the alteration of form may be at first, yet the moment a slight alteration has taken place, the destructive change then goes on in an accelerated ratio. And here a very important distinction should be observed, which is, that when the force is exerted within a tube tending to burst it outwards, the force exerted will not induce any change of form such as to render the tube weaker; because if the tube was originally made tolerably near to the true figure of resistance, any change of figure which afterwards takes place, must be such as

experiments were made to ascertain the relative force which copper tubes were able to support internally and externally: the tubes were beautifully made, and as perfectly cylindrical as hands could form them, but it was found in every case that a much less force was sufficient to crush or collapse the tube than what was required to burst it asunder.