RAILWAY ACCIDENTS, &c. 



[1852. 



on a bauk of fog, and even on the bubbles of a small brook. 

 Professor Necker describes another beautiful phenomenon, the 

 explanation of which must be referred to the same piinciple; 

 " If the Sun is rising behind a hill covered with trees and brush- 

 wood, a spectator just within the verge of the shadow of tlie hill 

 will see all the little branches thrown into relief against the sky, 

 not, however, dark and opaque, but glowing with a white bril- 

 liancy like silver, even to the depth of several feet bebw the 

 summit of the hill." 



When the suspended aqueous vapour is condensed and descends 

 in the form of rain, it gives rise to the splendid and familiar spec- 

 tacle of the rainbow. This consists in general of two circular 

 and concentric arcs, separated by a dark interval of about 8° 

 breadth, the outer one being much the fainter of the two, and 

 each exhibiting the prismatic coloui-s, in the inner the violet being 

 on the inside while in the outer the order of colour is revereed. 

 The fii-st person to point out the origin of the bows was Antonius 

 de Dominis, Archbishop of Spalatro, in 1611, A. D.; his expla- 

 nation y/as appropriated by DesCartes, but as the true theoiy of 

 colours was not at that time known, it was left for Newton to 

 give a full account of the phenomenon. It was by him shewn, 

 beyond doubt, that the inner or primary bow is formed by the 

 Sun's rays which reach tlie spectator's eye at emergence from the 

 rain-drops under the angle of least deviation after one internal 

 reflexion, and in like manner the outer or secondary bow by these 

 emerging after two internal reflexions. So also a tertiary bow 

 would be formed after three such i-eflexions, surrounding the Sun 

 with an angular radius of 40° 21', but the light is so much 

 diminished at each successive reflexion as to be too faint to make 

 any impression on the retina, and this bow has consequently never 

 been seen.* In some instances a colomed arch has been seen 

 between the two bows, and not concentric with them, aiising 

 undoubtedly from the reflexion of the lower part of the primary 

 bow which falls below the horizon at the surfaxje of a river or 

 lake. Sometimes, also within the primary and outside the 

 secondary, are seen successive coloured bands, being of a reddish- 

 purple in contact with the violet of the bows, then green, purple, 

 and so on in the order of Newton's rings. Young shewed that 

 these resulted from the interference of rays which undergo the 

 same deviation at angles of incidence a little less and greater than 

 that which furnishes the ray of least deviation. Lastly, Mr. 

 Airy, having observed that the greatest intensity of illumination 

 does not occur exactly in the place indicated by the geometrical 

 construction, has investigated the whole subject as a problem of 

 interferences on the undulatory hypothesis, and his results have 

 been fully verified by the experiments and measurements of 

 Professor Miller, so that the theory of the Rainbow may now be 

 said to be complete. 



Similar appearances ought to be produced when the Moon is 

 the illuminating body, but" her light is so much fainter than that 

 of the SuH as to render the occurrence even of a primary bow 

 very rare ; so far as I am aware, the secondary and supernumerary 

 bows have never been seen. 



To he continued. 



Railway Accidents; tltcir Cause and Means of Prevention; 

 detailing? particularly tlie various contrivances wliicli 

 are in use, and liave been proposed; witli the Regula- 

 tions ot some of the principal Lines, by Capl. 1*1. Ilnisli. 



(Read before the Inslitulion of Civil Engineers.) 

 The author first considered those points connected with the 

 road, and the machinery employed upon it, from which loss of 



• Tliis is contrary lo the .statement of Dr. Lloyd, who says that tertiary 

 rainliows have been observed ; he liowever refe's to no particular instance, 

 and 1 certainly have never lieard o( one. M. Babinel, an ac ule observer, 

 was unable under the most favorable citcumslances to perceive the faintest 

 trace of one. 



life and injury to person and property most generally arose. 

 With regard to the road, or permanent way, from which fewer 

 accidents occurred than from any other cause, its complete cflTtn;- 

 tivencss was the basis of all safety in railway travelhng ; and for 

 keeping it up, constant vigilance was necessary, especially when 

 any great and sudden change of weather took place, as then the 

 weak points were sure to show themselves. It was a very rare 

 occiirrence for trains to run off the line ; and when they did so, 

 it was more genejally due to obstructions designedly placed 

 on the line than to any neglect of the superintendents or 

 the platelayers. With raspect to the rolling stock, it appeared 

 from a return of one thousand cases of engine failures and 

 defects witliin two years on the London and North- Western 

 Railway, that burst and leaky tubes nearly doubled any other 

 class of failure ; and that these, with broken springs and broken 

 valves, amounted to one-thhd of the whole number ; and though 

 they caused no direct danger to the public, yet as producing a 

 temporary or permanent inability of the engine to carry on its 

 train, they might be the remote cause of collision. These 

 and other circumstances had led many persons to suggest 

 various contrivances for communicating between the passengers, 

 the guard, and the engine-driver, almost all of which were iden- 

 tical in princijile, consisting of a connecting wire or rope. This 

 plan had been tried and failed. A more feasible and favourite 

 one was that recommended by the Railway Commissioners, which 

 was to continue the foot-boards, so as to form a narrow platform 

 from end to end of the train, but a committee of railway officials 

 had subsequently expressed then- unanimous condemnation of the 

 measure. The plan now adopted on the London and North- 

 western Railway, was, for the guard's van, at the end of the train, 

 to project about a foot beyond the other carriages, so that the 

 guard looking through a window in this projection might notice 

 the waving of a hand or a handkerchief; this was, of course, 

 useless at night. All these causes, however, did not produce a 

 tithe of the accidents which resulted from a want of attention to 

 signals atid a neglect of regulations, which of all sources of danger 

 were the most prohfic. The Electric Telegraph had greatly 

 facihtated working under variable circumstances, and so beneficial 

 had its effects been, that during the year 1851, out of V,000,000 

 passengers, or nearly one-third of the population of England, who 

 had travelled over the London and North- Western RaSwa}', only 

 one individual had met with his death (from which casualty the 

 author also suftered) and this was the eflect of the gravest diso- 

 bedience of orders. In the six months during which the Exhib- 

 ition was open, 775,000 persons were conveyed by excursion 

 trains alone, in 24,000 extra carriages, all centering in a single 

 focus, arriving at irregular hours and in almost unlimited num- 

 bers, from more than thirty railways, without the most trifling 

 casualty, or even interruption to the ordinary extensive business 

 of that line. The author thought undue importance had been 

 attiiched to the question of irregularity in the times of the trains, 

 as an essential element of safetj', for with perfect signals and a 

 well disciplined staft' no amount of irregularity should lead to 

 danger; but, on the contrary, it should, to a certain extent, by its 

 very uncertainty, induce increased vigilatice, and therefore greater 

 safety. Accidents veiy rarely happened frotn foreseen circum- 

 stances, but generally from a simultaneous conjunction of several 

 causes, and each of these was provided for as it iuose. The 

 statistics of railways, and the periodical publication of the Gov- 

 ernment returns, drew public attention very pointedly to the 

 aggi'egato of accidents ; but it was believed that if due regard 

 was had to comparative results, if the accidents to steamers, or in 

 mines, to omnibus passengers, or even to pedestrians, were as 

 carefully recorded, that then, whether as regarded the ease and 

 celerity of transit, or the facility of conveying nutnbers, the rail- 

 way system, even in its present state, would be found to be 

 incomparably safer than any other system in the previous or 

 present history of locomotion. 



