.1847.] 



THE CIVIL ENGINEEERAND ARCHITECTS JOURNAL. 



9 



WILD'S RAILWAY SWITCH. 

 (With an Engraving, Plate III.) 



In the present number we give an engraving of a new railway 

 switcli. Tbere have been since the first introduction of railways, 

 several arrangements proposed for passing trains from one line of rails 

 to another ; the whole of these, however, which have been adopted 

 may be classed under two heads: those in which, in order to eflfect a 

 change from one line of rails to another, the apparatus had to be 

 moved by hand ; and those in which an engine can pass from either of 

 the two diverging lines on to the single line without such aid, clear- 

 ing the way for itself, should the switch be in the wrong position. 

 These are termed, and are, to a certain extent, self-acting. 



The former possessed the advantage of making Ihe guage perfect 

 for either line, but was deficient in the more essential quality of safety; 

 while the latter, to attain this quality, sacrificed the parallelism of 

 gunge. In the improved switch the advantages of both are united, 

 the self-acting principle being accompanied with perfect uniformity 

 of guage. 



In order to describe the working of the new apparatu?, it will be 

 first advisable to refer to the one now mostly employed, in vi'hich 

 either tongue rail is embedded in the ordinary rail according to the 

 position of the switch ; in this arrangement the guage is always im- 

 perfect, as the notch occupied by the end of the tongue rail is, when 

 this is withdrawn, left exposed : this defect is partially provided 

 against by the introduction of a check rail. 



In the improved switch, the end of the tongue, when in contact with 

 the rail, is also embedded in a notch, which however ceases to exist 

 when it is no longer required, "his motion is effected by causing the 

 rail abutting against the end of the tongue to move in connection witii 

 it, but in the opposite direction, so that when the tongue is with- 

 drawn, the protruding mil which formed the notcli is withdrawn also. 



In all inventions of this class, however ingenious they may appear 

 on paper, practice is the main test of their utility, and we are informed 

 that the invention which we have now noticed, has been for some 

 time in successful operation upon several railways; among which we 

 may mention the Grand junction, the Manchester and Leeds, the 

 Chester and Birkenhead, and the South Eastern Railways. 



THE PLANET BEYOND URANUS. 



The memoir of the discovery of the planet beyond Uranus, read by the 

 Astronomer-Royal at the November meeting of the Royal AsUouomical 

 Society, has been printed on account of its importance before the remain- 

 der of the usual monthly notice was completed. Extracts of Professor 

 Airy's memoir are given below, but for the sake of brevity several parts 

 are omitted, for which we have substituted the paragraphs in brackets. 



We wish to direct the reader's attention chiefly to the papers marked 11 

 and 12, and to the remarks following them. It will be seen from these, 

 that a few days after INIr. Adams had communicated to the Astronomer- 

 Royal all the elements of the planet, I\I. Le Verrier published, in the 

 Comptes Rcnitus, a paper on the perturbations of Uranus, in which he says 

 nothing ot" their being caused by an exterior planet: we may, therefore 

 suppose that he had not, at ihat time, made any discoveries respecting it. 

 Seven months after, M. Le Verrier publishes another paper, in which he, 

 for the first time, speaks of the new planet. The Astronomer-Royal says 

 that he received this paper with " a feeling of delight and satisfaction," 

 because it confirmed the conclusions of Mr. Adams respecting the position 

 of the planet, which he " had perused seven months earlier." It is im- 

 portant to observe that this second paper by M. Le Verrier gave only the 

 position — not the mass and orbit — of the planet, which had been however 

 ascertained by Mr. Adams. The eccentricity of the planet was not dis- 

 covered by M. Le Verrier till August, 1846 — that is, ten months after the 

 Aatronomer-Royal received Mr. Adams's determination of it. 



It appears that neither the Aslrooomer-Royal nor Professor Challis 

 thought it worth while to take the trouble of looking for the planet until 



Le Verrier's paper confirmed that of Mr. Adams. The self exculpatory 

 tone adopted by the superintendents of the two principal English observa- 

 tories, does not seem altogether needless. The fact of their both olfering 

 apologies, seems to indicate that apologies were necessary. The Astrono- 

 mer-Royal had *' always considered tiie correctness of a distant mathema- 

 tical result to be a subject rather of moral than of mathematical evidence." 

 Professor Challis says, in a paper following that by Professor Airy, 

 that his motive for undertaking the search for the predicted planet, was 

 the agreement of M. Le Verrier's " deductions with those of Mr. Adams, 

 together with the recommendation of the Astrouomer-Royal." He tells 

 ns, also, tiiat he was deterred from commencing the wurk sooner, because 

 it was "so novel a thing to undertake observations in reliance upon merely 

 theoretical deductions." 



We have no desire to depreciate M. Le Verrier's labours. On the con- 

 trary, they entitle him to high renov?n. His first paper alone, investi- 

 gating the perturbations of Uranus without asssigning a new cause for 

 them, is a work of the utmost scientific value. But the chief peculiarity 

 of this event in the history of science is the predictive evidence and appli- 

 cation of the laws of gravitation. Hitherto, the evidence of the truth of 

 those laws, wonderfully minute and varied as it has been, was restricted 

 to the explanation of observed facts ; but the most overwhelming evidence 

 of a theory is its capability of anticipating Ihe result of experimental ob- 

 servations before they are actually made. This kind of evidence is fur- 

 nished in an unexampled degree, by the anticipatory calculation of the 

 mass, &;c , of the unseen planet. Regarding, therefore, the prediction of 

 the planet as an event altogether unparalleled, and as the feature of the 

 discovery most important with respect to the evidences of science, we 

 cannot over-estimate the value of the fact established by the Astronomer- 

 Kojal, that Mr. Adams was the first predicter of the position, mass, and 

 orbit of the new planet. 



When the Astronomer-Royal speaks of the discovery as "a consequence 

 of what may properly be called a movement of the age," we must take 

 this as a rhetorical expression, not intended to have any specific meaning. 

 In (act, the utmost that can be made of the sentence is this, that there has 

 for some time existed a general suspicion of the existence of a planet 

 beyond Uranus. The numerical determination of the longitude of the 

 planet (323 34), &c., by an elaborate mathematical investigation, required 

 something a little more tangible and definite than a " movement of the 

 age." 



It has not been usual to admit into the Memoirs of this Society mere 

 historical statements of circumstances which have occurred in our own 

 times. I am not aware that this is a matter of positive regulation : it is, 

 I believe, merely a rule of practice, of which the application in every par- 

 ticular instance has been determined by the discretion of those Officers of 

 the Society with whom the airangement of our Memoirs has principally 

 rested. And there can be no doubt that the ordinary rule must be a rule 

 for the exclusion of papers of this character ; and that if a positive regu- 

 lation is to be made, it must absolutely forbid the presentation of such 

 histories. Yet it is conceivable that events may occur in which this rule 

 ought to be relaxed ; and such, I am persuaded, are the circumstances 

 attending the discovery of the planet exterior to Uraiiits. In the whole 

 history of astronomy, I had almost said in the whole history of science, 

 there is nothing comparable to this. The history of the discoveries of new 

 planets in the latter part of the last century, and in the present century, 

 offers nothing analogous to it. Urnnus, Ctres, aad Pallas, were discover- 

 ed in the course of researches which did not contemplate the possible 

 discovery of planets. Juno and Vesta were discovered in following up a 

 series of observations snggested by a theory which, fruitful as it has been, 

 we may almost venture to call fanciful. Astrwa was found in the course 

 of a well-conducted re-examination of tlie heavens, apparently contem- 

 plating the discovery of a new planet as only one of many possible results. 

 But the motions of Uranus, examined by philosophers who were fully 

 impressed with the universality of the law of gravitation, have long ex- 

 hibited the efi'ects of some disturbing body : mathematicians have al length 

 ventured on the task of ascertaining where such a body could be ; they 

 have pointed out that the supposition of a disturbing body moving in a 

 certain orbit, precisely indicated by them, would entirely explain the ob- 

 served disturbances of Uranus : they have expressed their conviction, with 

 a firmness which I must characterise as wonderful, that the disturbing 

 planet would be found exactly in a certain spot, and presenting exactly a 

 certain appearance ; and in that spot, and with that appearance, the planet 

 has been found. Nothing in the whole history of astronomy can be com- 

 pared with this. 



The principal steps in the theoretical investigations have been made by 

 one individual, and the published discovery of the planet was necessarily 

 made by one individual. To these persons the public attention has been 

 principally directed ; and well do they deserve the honours which they 



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