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Chairman and Directors of the Company, as well as the Coroner, to investigate the subject with more than ordinary attention.

Conformable with these instructions, I visited the spot where the accident occurred, and from a cursory view of the upper part of the copper fire-box, it appeared as if an old crack or flaw had been present, and that part being the weakest would, as a matter of course, be the first to give way. A closer view of the ruptured parts, however, proved this impression to be erroneous, as by careful inspection the copper was found not only perfectly sound, but free from cracks and flaws of every description. This conclusion was fully confirmed on comparing the edges of the plate, which on one side gave indications of an old crack, with the corresponding part from which it was torn. By this comparison it was found perfectly sound throughout the whole length of the fracture and thickness of the plate; but it did not account for the discoloured appearance of the fracture on the opposite side of the plate, which, as before stated, indicated an old crack. A little reflection will, however, shortly explain this apparent discrepancy, and that particularly if we bear in mind the position of the plate, and the nature of the rupture where it first gave way, and where it was ultimately forced down like a piece of paper upon the front of the tubes. If, for example, we suppose the incumbent pressure of the steam to be greater than the resistance of the plate which forced the top off the fire-box, the result would be a forcing down of the weak part and a subsequent and rapid, if not almost instantaneous, rupture of the whole of that part, and an equally rapid turning downwards. of the two others which form the rectangle of the fire-box. Now in the act of tearing, it is obvious that the steam and water would be discharged with great force upon the fire, which mixing with the gases and carbon of the furnace, would form a coloring matter sufficient to give those appearances to the fractured edge of the descending plate. From this it is evident that the present appearance of the ruptured edge of the plate is no indication of unsoundness in the material, which is fully proved by the clean and perfectly solid metal from which it was rent at the top bend of the fire-box on the opposite side.

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Having shown that the accident did not arise from any defect in the metal of the fire box, I would now request attention to the iron bars or stays which extend longitudinally over the metallic cover of

the fire box. These stays are seven in number, and 4 inches deep in the middle, by 14 thick, and are strongly riveted with seven bolts, through the copper of an inch thick. These seven supports were fixed equidistant from each other or about 6 inches apart from centre to centre. They are also 3 feet 4 inches long, and rest upon the dome, as in figure 1.

From this it will be seen that the stays or bars were of an inch shorter than the length of the fire box, owing propably to the rounded corners of the dome, which did not admit of the ends of the stays fitting upon them. Now in seeking for the cause of the accident, from defects in these parts we shall find ourselves equally at a loss in accounting for results as we were in our previous disquisition on the quality of the copper which may be proved by calculations as follows:

Suppose each of the malleable iron stays, supporting the roof of the fire box, to be a series of separate beams or girders subjected to a given strain, and taking each as equal to a beam whose bearings are 3 feet 4 inches asunder, we then have a compound beam of malleable iron, and copper of the dimensions as in figure 2.

Now as the pressure is uniform and equally distributed over the whole surface, we have by the formula (after allowing for the difference of the strengths in the metals,) a force of 20.7 tons as the breaking weight, uniformly distributed over the surface. This calculation is made under the supposition as if each of the bars were subjected to a separate strain, whereas they are connected by the union of the lower flanches, thus giving a resistance in every direction to the internal pressure from above. If we, therefore, take each of their separate efforts to resist a destroying incumbent force at 20 tons, we then have 20 × 7 = 140 tons as the ultimatum pressure for separate beams, and supposing double strength to be gained by the union of their lower flanches of solid copper, the correct resisting force of the top of the fire box to rupture would then be 280 tons. Now 60 lbs. on the square inch would give 43.35 tons acting upon the top of the fire box; and hence would follow a pressure of 387.6 lbs. upon the square inch, which would be required before the top of the fire box and its supports could give way.

As a further proof of the strength of this part of the structure, let us again take the tensile force of copper (which of the best quality is about 23 tons to the square inch; but, taking it at 20 tons,) and it will be found that the resisting force to the rupture of one side alone will be about 310.8 tons. It is therefore obvious, that in order to force down the top of the fire box (on that side which apparently first gave way,) a force of 310 tons would be required, and an equal force of 280 to 300 tons would be necessary to break the iron stays or bars supporting the cover of the same.

Having endeavoured to establish the fact of sufficient strength in the ruptured parts of the material, and having explained the nature of the construction, so as to show that the accident could not arise from that cause, I would now respectfully direct attention to another part of the subject which appears to me to bear directly upon the ques

tion. It must appear obvious to every person conversant with the subject, that a heavy body, such as a locomotive engine, of 15 to 16 tons weight could not be projected to a height of 25 to 30 feet, without the agency of an enormous force. That power could not be maintained by the strength of the material, nor yet by its distribution, however well-arranged, in the construction. We must, therefore, look for it in some other quarter, and endeavour satisfactorily to prove, that the effects exhibited in this lamentable occurrence, do not, in any instance, disagree with the causes which produced them. In this inquiry, some curious and interesting scientific phenomena present themselves. First, to account for the instantaneous elevation of such a ponderous body as a locomotive engine, to a height of 30 feet; and, secondly, to demonstrate and explain the causes which produced that elevation.

In approaching this investigation, it would require the aid of a profound mathematician; but, that being a work of time, I must trespass upon the patience of the jury whilst I endeavour to make the most of what I have got, and to show, that the task is probably less difficult than appearances at first would indicate.

An eminent writer on mechanical philosophy states, "that forces are of themselves imperceptible, and are seen only in their effects, or what measures they effect." Now, according to the laws of gravitation, that force which accelerates the descent, and retards the ascent of a body, must be considered as a constant uniform accelerating or retarding force. Therefore, the motion of a falling body projected downwards, is uniformly accelerated, and that of a body projected upwards, is uniformly retarded; that is, the required velocities are as the times in which they are acquired by falling, and the extinguished velocities are as the times in which they are extinguished. Hence it appears, that the spaces described by a falling body, are proportional to the squares of the times, from the commencement of the fall, and the spaces described by bodies projected upwards, are as the squares of the times of the ascent. It therefore follows, that the same laws that govern the descent, also regulate the ascent of bodies; and, having these fundamental principles in mind, I apprehend we shall find less difficulty in solving the question by the simple law of projectiles. Taking, therefore, the forces of projection as equal to those of gravitation, and supposing a body such as the locomotive engine in question, 15.5 tons, falling from a height of thirty feet (which may fairly be taken as the height of the ascent,) we then have the square of 30 = 5.473 X 8 = 43.780 for the velocity in feet per second, or as the force with which a heavy body falling from that height would strike the ground. Now assuming the force of impact to be as the velocity multiplied into the weight of the falling body, we again have 43.780 x 15.5 X 2240 1520041.6 lbs., or 655.7 tons, as the momentum or measure of contact with which a body of that weight would strike the ground in its descent from a height of 30 feet. Let us now reverse the proposition, and suppose, that instead of an uniform accelerating motion produced by gravity, we have to encounter its equally uni form functions of retardation; it then follows that the same momentum VOL. IX, 3RD SERIES-No. 5.-May, 1845.

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of force with which the descent was terminated, would be required to raise it to the same height. It is therefore, evident, upon this hypothesis, that a projective force of 1520041.6 would be required to elevate an engine of 15 tons to the actual height of 30 feet, in order to demolish that part of the roof removed by the explosion.

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Let us now compare the forces of projection, or the powers which operated, upon the engine in its elevation to the height already named; and it will be found that 1563821 ÷ 1619.5, the area of the fire box in square inches 939 lbs. upon the square inch. Now this pressure is more than double the strength of the fire-box, or any parts of the boilers containing the elastic force; but supposing the top to give way with 250 to 300 lbs. on the square inch, it then follows that the additional force must have been generated in the act of the explosion, by the intensely heated water and steam rushing upon the fire at a considerable higher temperature. We are all acquainted with the effects of water thrown upon a red hot fire, and the explosive nature of the volatile vapours which are thus generated by the combined action of the gases and water. The effects would be more tremendous in the case before us as the water in the boiler contained, previous to the discharge, a large proportion of heat, and the calorific effects would be a proportional to the pressure of the steam at the time when the rupture occurred.

I am not sufficiently acquainted with theoretical chemistry, to prove that this solution is correct, but I am happy to find most of my professional friends agree with me in that opinion; and, in the absence of more convincing proofs, I am disposed to consider the reasons and demonstrations already given, as the cause of the accident, which I regret to find has been attended with the loss of life.

As a further corroboration of these views, I may perhaps be permitted to advert to the prodigious power of fixed gunpowder, which is nearly 1000 times greater than that of the atmosphere, which, taken at 15 lbs., gives the enormous force of 15,000lbs. or above 6 tons to the square inch. This is very far above our computation, and looking at the position of the engine and the depth of this fire box, we may readily compare it, along with the pit below, to the breach of a mortar in throwing a shell, whence the projectile is discharged instantaneously on the firing of the powder, and the elastic force of the expended fluid. Such was nearly the case with the Irk, which, on the instant of the explosion, left at the bottom of the pit indelible impres sions of a powerful recoil.

Viewing the circumstances of this extraordinary case in all its bearings, I am led to the conclusion that the question resolves itself into two considerations in connexion with the cause of the accident. First, that the top of the fire box was forced down upon the furnace by excessive pressure arising probably from accumulated force of the steam having no outlet through the safety valves; and secondly, by a process of inductive reasoning from the force of a body of water and vapour, at a high temperature, being discharged upon the evolving gases and glowing embers of the furnace, whereby the carburet

ted hydrogen, and carbonic oxide gases, were charged with their equivalents of oxygen, and explosion ensued.

The above appear to be the only principles upon which we can account for the extraordinary effects indicated in the rupture of the metallic plate in the first instance, and ultimately in the explosion and subsequent force which carried the engine from its primary position to the place where it now rests.

In closing these observations, I would respectfully intimate that the subject is one of vital importance, not only as regards the Proprietors and Directors of railways, but the public are deeply interested, and have a right to demand every security which the experience of the last 15 years can afford, either in the transit or the machinery by which that transit is effected.

It is for these reasons that I venture to recommend a searching inquiry into every circumstance connected with the present accident, and conceiving that a full and complete elucidation of this subject may not, on this occasion, be afforded, I would further suggest that a series of well conducted experiments be entered upon for the purpose of ascertaining the cause which led to the present and late accidents on the South Eastern Railway, and for determining some fixed principle of action whereby the lives of the public may be secured, and the Proprietors of railways relieved from a tax which bears with equal severity upon their reputation as well as upon the revenues of their establishments.

In the acquirement of these objects a mass of valuable information would be obtained, and our knowledge of an intricate subject greatly extended, to say nothing of the advantages which this enquiry would confer upon science. If done at all, it should be done at the expense of the different Railway Companies; and probably it could not be entrusted to better hands than the British Association for the advancement of science.

In answer to the questions of the coroner, he said he did not attribute the accident to the shortness of the longitudinal bars in the fire box. He examined the spring, balance and valves, and they appeared good. He said one of the valves was at the command of the driver, and could be screwed down by him; if he had done so, and the safety, or lock-up valve, had been down also by any unknown cause, an explosion would, as a matter of course, follow. He said the same consequence would ensue if only one of the valves had been closed, provided the steam was generating very rapidly. He heard that, for the purpose of getting up the steam very fast, the valve, at the command of the driver, had been screwed down. From what he saw of the fire box, it appeared perfectly square and sound, as well as all parts of the boiler. He looked, he said, very carefully-at first it appeared as if part of the fire box had been cracked; but on comparing the fractured parts, it was afterwards found the copper had every appearance of being sound and good metal, and of sufficient strength. Mr. F. said the Irk was made in January, 1841, and had been in the use of the Company from that time. The driver, he said, could not screw down the lock-up valve. The lock-up valve would have

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