way, over the sleepers, a considerable distance, until the tremendous shocks broke the fore-axle and brought all to the ground. This statement clears up most of the mystery about the accident: it satisfactorily accounts for the failure of the fore-axle, although the iron, by acknowledgment, was of the best quality; and it particularly explains how it came to be broke at both ends. This event is now seen to be the last, instead of the first of the series, as assumed in the official investigations, and as taken for granted on such authority, in all the subsequent discussions. saga But how was it that no notice was taken, by the authorized reporters upon the accident, of the observations and inferences made by this engineer? Did he not come within the purview and cognizance of official and scientific dignity; or were those personages really incompetent, however mathematically clever, to appreciate inductive truth, or the manner of its evolution, through a material investigation of physical incidents, even when presented to them by others ? It is surely better to impeach their city than their integrity, in a matter of so much importance, and thus save them from the imputation of a design to suppress information on a subject on which the lives of thousands may depend on its being thoroughly and faithfully inquired into, while time and circumstances permitted M. Combes is a good mathematician, and can give mathematical, if not practical formula for the velocity of a current of air in the ventilation of mines; he is, moreover, the superintending government engineer of steam-engines in the department of the Seine; but in spite of all this, and in spite of the very best Ecole Polytechnique attainments, into which a man can be drilled, he does not appear to have been aware, that a six-wheel locomotive will as surely come to the ground as a four-wheel engine, in case a similar accident happens to its fore-axle as that which he supposes occasioned the late disaster; for he says in his report, what a little practical good sense, if not common sense, would have informed him to the contrary, that, "if one of the axles (provided six wheels are adopted) should break, the carriage would still rest on supporters, and continue its course." This would be true only in the contingency of the working axle being the one that failed. If either of the 483 others gave way, the want of equilibrium, if not determined at once by the inequality of weights, would be quickly determined either by the tug of the engine or the push of the train, according as the one or the other of these causes was brought into action, through the failure of the fore or of the hind axle, as the case may be. There is, however, one important point leading locomotive leave the rails in connot yet cleared up, which is this: did the sequence of a failure occurring in any part of the engine, or in consequence of oscillatory motions ordinarily induced ? The latter is the conclusion come to by your correspondent, and probably also by the French engineer whose investigations he has recorded; but it does not appear to me that the evidence is in favour of it, but leads rather to the opposite opinion. It must indeed be allowed, that the existence of very violent oscillations both vertical and lateral, after proved, by the alternate indentations of the engine left the rails, is unequivocally the wheels on the sleepers, and by the sinuous lines so traced. It must also be admitted, that this freedom of oscillation, and the measured correspondence of the indentations with the width of the wheels apart, are, both of them, incompatible with a complete fracture of either of the position of the wheels in consequence of axles; or at least with any very deranged it. It must be further admitted, that these oscillations could not have committed, that they existed some time premenced all at once; and it may be adviously to the locomotive leaving the rails, increasing gradually in violence to such an extent, as to induce M. Milhan to sound the alarm whistle, and Mr. George to apply the brake. But still the question arises, whether these were not the themselves sufficient to have forced the ordinarily induced oscillations, and not of something else did not occur, in concurengine off the rails? Whether in fact rence with, and perhaps also in aggravavation of, these oscillations, to occasion the wheels to leave the rails? know that the following incident occurred, possessing an aptitude to stand in the relation of a cause to the accident, whether it actually did so stand or not, plied the brake immediately previous to namely, that Mr. George suddenly apits occurrence. Now we I endeavoured to show in a former article, (No. 981,) that the suddenness and force of this application may have thrown a stress of so instantaneous a nature on the axle, (not knowing at the time which axle had given way,) as to occasion its fracture, and that thus the disaster had occurred. Subsequent information, chiefly furnished by your correspondent, a "Practical Engineer," whilst it obliges me to modify, in some measure, this hypothesis, confirms, I think, its accuracy, as to the orgin of the accident being in the application of the brake. The fracture of the fore axle in two places is now amply accounted for, but the breaking of the driving axle is not so easily understood. It must either have been a mere casualty (another name for obscure causation and our own ignorance,) or it must have taken place at the overthrow of the engine; or it must have been produced by the brake. The first supposition is quite a chance, and unlikely to occur at a time when the working strain on the axle could not have been great; the second, also, is a very improbable occurrence, except so far as the shock and collision may have made a complete fracture of a previously crippled state of the axle; for it is particularly to be observed, that the axles, neither of the accompanying tender, nor of the six-wheeled engine and its tender, were broken in this melée. Besides, it is expressly stated in the report, that "the fracture appeared to have been produced by torsion." Only the third supposition, therefore, is probable, and it alone furnishes an adequate cause for the effect. There must have existed in some manner an obstacle to the rotation of the driving wheels, equal in its force of resistance to the power of producing torsion in the axle. Now I cannot conceive anything in the way of friction from the ground, or from carriages in contact, that could have furnished such resistance. Nothing but the means expressly provided in the brake, for putting a complete stoppage to the revolutions of the wheels, would be sufficient for the purpose. It appears to me that the application of the brake operated in this manner :At the same moment that an instantaneous strain was thrown on the driving axle, in the form of a retarding force to oppose the mass in motion, one of the cranks was with equal suddenness necessarily caught at, or very near to, a right angle with the connecting rod, and thus the steam being on, the axle was acted on by a double force, transverse and tangential, to the effect of both bending and twisting it at one end. Thus the appearance of torsion was produced, (and it is not an appearance likely to mislead), although the complete fracture it is probable only took place on the overthrow and collision of the engines. Neither could the axle have been much bent, otherwise the derangement of the wheel on that side would have been greater than it appears to have been; but it was sufficient, I conceive, to constitute that accessory circumstance, which in aid of the violent lateral oscillation, occasioned the wheels to surmount and leave the rails. It is easy to see how this effect would be produced, and how in the operation the rail on that side would be forced into "the very sinuous state" described by your correspondent, for the tendency would be, so to bend the axle at the journal on the side where the torsion took place, as to place the wheel at a slight horizontal diverging angle with the rail. Hence the indentations on the sleepers, (the wheel being retained in that position by the brake), would not be observably different from the proper distance of the wheels apart; hence also the increased inclination to run off the rails; and hence the intermitting sort of displacement of one rail only from the straight line, as the oscillatory movement upon it took place. It appears also that the rail in this predicament was the right hand rail of the right hand line of rails, looking towards Versailles; and it might have been ascertained at the time, if that full investigation of the minutest particulars had been instituted, which the importance of the subject demanded: whether or not this was the rail which would be displaced, as corresponding to the position of the brake, if but one; or to the side on which Mr. George was standing, if there were two; or the crippled end of the axle, if, as is most likely, the crippling and ultimate fracture took place on one side. The several circumstances here noticed, combined and harmonised, strongly warrant the inference I have drawn, that the locomotive was forced off the rails by an accident supervening upon a state of oscillation; and that the origin of this accident, and the manner of its operation, were such as are here described. But the case will admit the further supposition, that the accident imparted additional force to the oscillatory motion, and therefore acted both directly and indirectly to carry the engine over the rails. It will also admit another supposition, that Mr. George-having brought the brake into action, and the axle having been twisted, and bent as before described, causing the wheel on that side to be thrown in some slight degree out of position-almost immediately afterwards released his hold upon it, and that thus the corresponding rail was at every revolution forced outwards, and consequently into that sinuous state described by your correspondent. This supposition might have been tested by measurements, showing whether or not the sinuosities coincided with the circumferences of the wheel. The case will further admit the possibility of the axle having been completely broken, if we suppose that the wheel with the shorter portion of the axle was kept stationary, and not greatly out of position, by the journals and by the jamming it received from the brake. In such a state of things, and the steam in the confusion not turned off, the oscillations would be very violent; for the engine would be urged against one rail, and take a rebound to be again urged and thrown off as before, until it overleaped the rails; and thus also in this way would only one rail receive damage in an intermitting manner, for the onesided propulsive action would protect the rail on that side. The great weight of the six-wheel engine behind, probably enabled it to keep to the rails to the last, and would prevent the other from deviating greatly from the track. Whatever may have been the exact course of the accident, the inference that the first event in the sad series was the application of the brake, and a consequent crippling or fracture of the driving axle, is, I consider, a matter of the highest probability. How this further operated to bring about the subsequent results, is more a matter of conjecture; but I have pointed out three modes in which they may have been produced, each consistent with the observed appearances, and quite adequate, in combination with a state of oscillation, to force the engine off the rails; but after this event, the occurrences are no longer conjectural. The indications are quite demonstrative, that the final event was the double breakage of the fore axle, and that it was occasioned by the concussive shocks it received, through the leaps and boundings of the engine over the sleepers. If, as hitherto considered, this event had been the first, it would also have been the last, for a necessarily immediate overthrow must have been the result; but all the appearances prove, however differently they may be interpreted, that time and distance were occupied in bringing about the catastrophe. The series of events, as I have given them, are, I think, just such as would with the greatest probability occur; they are in conformity with all the indications; and are consistent in order, with the comparative and with the relative strengths of the forces and resistances brought into collision. I may probably in another communication take notice of some of the causes which occasion oscillation in railway engines and carriages; and also make some remarks on the ultra-scientific notion, which would trace the fracture of their axles to some occult electro and thermomagnetic influences. I am, yours, &c. BENJAMIN CHEVERTON. MR. ZANDER'S TABLE OF THE PERFORMANCES OF VESSELS ABOVE BRIDGEMR. ZANDER IN REPLY TO MR. BIRAM. Sir, I beg you will do me the favour to insert in your valuable Journal, a few remarks in reply to these of Mr. Biram, in your No. 1004, on my Tables of the performances of River Steam Vessels, (Nos. 1001 and 1002.) In those Tables, and the accompanying remarks, it is clearly shown that 24 floats in each wheel may be immersed in the water, or 5 floats in the two wheels, which will be equal to an area of 25 square feet paddle surface, acting on the water. Mr. Biram thinks I am in error, in regarding only the immersed paddleboard surface "as effective paddle-board surface:" I will explain my reasons for doing so. When the wheel is in motion, one part of the paddle-board surface is in the water, and the remaining part in the air; but as only that surface which is in the water serves to propel the vessel, I think it may very properly be called the "effective paddle-board surface." I now come to a point very deserving investigation. What value, as an effective means of propelling a vessel, do these paddle-board surfaces possess? Or in other words, what useful resistance does the water oppose to these paddle-board surfaces, compared with what the same surfaces would experience if moved in a perpendicular direction ? Mr. Biram will find that I have avoided giving any opinion on this question; seeing the disturbed state of the water in which the float moves, I regard the ordinary theory for calculating the useful effect of a paddle-wheel moved in the water, as being, if not useless, at least so complicated, that experiment alone can lead us to any correct practical conclusions on the subject. I have in my Tables given practical results only; I am convinced, that if other persons were to do the same, we should soon have such a collection of facts, formed under every variety of circumstances, as would enable us to deduce some certain rules for computing the useful effect of paddle-wheel surfaces. It is the more desirable to arrive at this knowledge as the proper proportion of the paddle-wheel to the vessel itself has so much influence in Steam Navigation. Trusting that the preceding explanation may serve to remove the doubts entertained by Mr. B. of the correctness of my Tables, gested to the Companies to stop the supplies, even for one day, of their lifedestroying commodity; but that they have all recommended only the straining of it through their own or their friends' filters, to prevent our stomachs being made the common sewer of all the impurities which are washed from millions of hands and backs in the great London (wash-hand) basin. I believe that all this fuss has its chief origin in those baby-exhibitions of solar microscopes, whereby the Polytechnic proprietary, in their zeal to amuse the children-philosophers, have taught the grown-up babies also, that pure crystal water is nothing but a mass of moving life and ravenous ten feet monsters; which they have done by crowding the larvæ of gnats and flies, and other water insects from a quarter to half-aninch in length, into the dirtiest ditch water. Now all this, however silly, is very harmless, so long as it is confined to flattering the conceit and furnishing the gossip of West-end philosophers; but I am very averse to have my constitution reformed, by such whiggery in water-drinking. I have lived a great part of my life for the last forty years in London, under the treatment of Sir Hugh Middleton; and finding myself still sound under his treatment, I am not particularly anxious to begin at this time to put myself under the new hydropathic system of the waterfilterers, who, by the way, I shrewdly and most polytechnically suspect, think that the pocket is a more vital part than the stomach in the human economy. I will mention one or two reasons why I fear, at this time, and upon this subject, to be over-philosophized. Your correspondent, Mr. J. Cole, (in your 1002nd No. p. 398) says, "such small filters, by the slowness of the process, destroy the carbonic acid gas which is contained in the water, and without which it speedily becomes offensive, and putrid, and injurious to health." Of course, Mr. Cole cannot be a friend to Mr. Stuckey and his instantaneous electrotelegraphic filter; but it strikes me with surprise, that while all the water-reformers have been taking for granted, that pure filtered water was the only elixir vitæ and required condition of long life, there should all at once start up a teacher-not one of their enemies either-who strikes a death-wound at their first premises, though so tenderly, it is true, that he, as it were, wounds them out of friendship. But the letting out of blood or water is not so easily stopped; and we are led at once to inquire,-if small filters abstract the carbonic gas entirely, may not more rapid filters do this mischief partially? And if one ingredient, carbonic gas, is a beneficial adulterater of the purity of water, may not some other of the component parts, which your correspondents propose to filter out, prove, after we have been disinfected of them, to have been equally beneficial? I will support this remark by an illustration, which, I hope, will serve to show that this subject of water-filtering is not quite such a matterof-course subject, and that it is not quite so certain and axiomatic that the purest water that can be by any means obtained is the most salubrious beverage. Your correspondent "A Subscriber," (in No. 1004, p. 430,) asks whether Mr. H.'s one-and-sixpenny filter "will take away the lime with which water, more or less, is impregnated, and which must be more or less prejudicial ?" Must lime indeed be prejudicial more or less? Why so, Mr. Editor? Must the sand and gravel that birds swallow be the killing of them? Must the iron, and silex, and lime, and other earths which the roots of vegetables drink up, be the destruction, or the saving of them? Are not our bones made up of lime? And where, if not from our food or drink, is this material of our architectural composition to come from? I do not mean to philosophize, or to account for these things; but I merely mean to say that they are difficult and intricate, and deeper than "must be," which is the only argument I have seen for the half of these things; and that I only hope that my life may not be made the sport of half a dozen of these "must be" and "would be" philosophers. Now, upon this subject of lime, a naval officer of experience was telling me, the other day, that they dare not give the pure rain-water which they catch from the skies to the sailors, for it would cause dysentery: they are obliged to put lime into it Bless me, Mr. Editor, what is become of our philosophers? I think I 487 see them all tumbling head over heels, in their confusion and flight, like so many thousand Chinese men-at-arms, upon They are obliged to put lime into it! the visitation of a two-and-thirty-pounder. But the water-filterers say, that water cannot be too pure; and "A Subscriber" says, "the lime must be more or less prejudicial." * Now, thank goodness, Mr. Editor, I am still cockney enough to bless the name of Sir Hugh Middleton, and to think him one of the greatest benefactors of the human race, in a joint stock company way that has ever appeared. But since it is plain that we are not much longer to be suffered to use the undisintegrated water of the silver Thames and the chalk-fed Lea, prepared in Nature's most perfect laboratory, I thank my stars ing the hand and wit of man as its instruthat, by the blessing of Providence, guidment, there are ample supplies of pumpwater in all parts of London, (inaccessible to the approach of filterers,) from which I myself, and my neighbours too, (judging by the number of pitchers that are seen carrying about just before the hour of dinner,) are supplied with all the unboiled water which we drink.† By the bye, Mr. Editor, no one of your correspondents has broached an essay upon the defecating process of boiling the water, which is so full of creeping things innumerable, and which process is so much in vogue already with all tea drinkers, in street and alley, at the cost of an eighteen-penny teakettle. Do these monsters survive this hot-bathing system, and do they come out renewed in appetite and mischief, from this Neptuno-Plutonic process? One thing I have been used to hear, ever since I was taught philosophy and fudge by the nursery-maid, that, by the chemical process of boiling in tea-kettles, the carbonic acid gas is driven off, which holds the lime in solution, and the lime falls to the bottom of the containing vessel; and, from the deposit of what is The river Lea, from which the New River derives much of its water, as well as the New River Head, has its source chiefly in the chalk formation, from which, it is well known, the most transparent springs of any flow, at all times, and in all places where chalk prevails. The reader will find in the article which follows this, some additional reasons for doubting the surpassing virtues of perfectly pure water.-Ed. M. M. |