THE CIVIL ENGINEER AND. ARCHITECT'S JOURNAL. 



69 



bearings, 13 wiih common transoms ; and that a more uniform and firm base 

 will be obtained, by depending on the weight of the trains to ultimately con- 

 solidate the base of the timbers, than upon any system of piling, presuming 

 always, that a proper and firm base is prepared in the first instance. 



The next consideration is, whether continuous timbers or isolated bear- 

 ings are preferable; the experiments on deflection show that there is a 

 greater amount of deflection on the continuous timber bearings on both the 

 Great Western and the Manchester and Bolton Railways, than on stone 

 blocks on the other railways ; the latter will consequently afford the least 

 resistance to the carriages; and the weight of the stone blocks intercepting 

 to a considerable extent the impact of the trains, they afford a permanently 

 firmer base. We have seen, however, that in hi^h rates of speed, the resist- 

 ance of the road itself is small, compared with the aggregate resistance ; and, 

 therefore, if continuous timber bearings are preferabll^ in wther respects, a 

 little additional friction cannot be of very great importance. 



There is no doubt that timber bearings produce less noise in the carriages : 

 and it has been urged with considerable force, that the wear and tear of the 

 engines and carriages are less than with stone blocks. I have endeavoured 

 to ascertain this, which is a very important consideration ; but the returns of 

 the expenses of the different railways do not, in my opinion, produce con- 

 clusive evidence on this part of the subject. The impression produced in 

 my mind by the information obtained, however, is, that with longitudinal 

 timber bearings of adequate rigidity and strength, the injury to the engine 

 and carriages will be less than with stone blocks. The case of the Dublin 

 and Kingstown Railway has been often quoted, as exhibiting an instance of 

 the great destruction to the engine and carriages, and road itself, by the use 

 of stone blocks; and the cross wooden sleepers in Chat Moss, and the 

 American railways, as iitstances of the utility and cheapness of keeping in 

 repair, the timber bearings. Every engineer, however, knows that the Dublin 

 and Kingstown rails were much too weak for the stone blocks on which they 

 were placed ; and the inferior rate of speed on the American railways affords 

 no criterion whereby to compare with the effect of stone blocks in this 

 country, where a much higher rate of sjieed is practised, — the peculiarity of 

 base of Chat Moss likewise, does not admit of any comparison with stone 

 blocks on a firm foundation. Notwithstanding this I am inclined to think, 

 that the wear and tear of the carriages and engine upon timber bearings of a 

 proper strength will be less than upon stone blocks ; — of the comparative 

 durability no definite comparison can yet be made. 



These experiments, however, show that the present scantling of timber on 

 both the Great Western and the Manchester and Bolton Railways, are much 

 too small for the loads which come upon them ; and that they do not present 

 a sufficiently rigid and unyielding base for a railway. One set of experi- 

 ments (No. 7, Parti. Book A-), on the Great Western Railway, on the 

 continuous timbers without piles gave very satisfactory results, but here the 

 scantling of the timber was 10 inches ; it appears to me, therefore, that if 

 continuous timber bearings are used, they should be of a scantling of timber 

 greater than that at present in use ; and it appears, also, that a more rigid 

 section, and greater weight of rail should be adopted. 



This will, no doubt, make the continuous timber healings more expensive 

 than stone blocks, against which we have less noise, and a smoother, and a 

 more perfect road for high rates of speed ; sufficiently strong continuous 

 timbers present, iu fact, a more perfect, but a more expensive line of road 

 than stone blocks ; — of the comparative durability no satisfactory conclusion 

 can be drawn. .4t a lower rate of speed, and where economy is an object, 

 stone blocks being cheaper, will be preferable. 



I have not in this i-omparison noticed cross timber sleepers, as compared 

 with continuous timber bearings ; as temporary roads, during the con- 

 solidation of embankments, the cross sleepers will be preferable ; but the 

 result of the experiments on deflection show, that there is not only a very 

 considerable yielding of the timbers, but that there is likewise an imperfect 

 fastening between the chairs and sleepers, which cannot be remedied without 

 increased expense and difficulty ; this road is much cheaper than either 

 adequately strong continuous timbers, or stone blocks, but it is less perfect, 

 and cannot be considered as a permanent description of road. 



With respect to that part of your request, which relates to the examination 

 of the Maidenhead Bridge; while on tile works in September last I minutely 

 examined the state of the arches and the plan of construction ; — the cause of 

 its failure appeared to me to have been occasioned by the centering being 

 prematurely drami, and before the cement was perfectly hardened and had 

 taken a set in the interior of the brickwork forming the ring of the arch. Mr. 

 Brunei at that time pointed out to me the remedies which lie proposed to 

 repair the defects, iu which I concurred, and those I understand have not yet 

 been completed. 



In conclusion, I trust that the magnitude and variety of the objects, and 

 the great and imposing interests embraced in this inquiry, added to the great 

 responsibility attached to the investigation, will be a sufficient excuse for the 

 protracted time occupied in making the experiments ; and I trust, also, that 

 these reasons, together with the unexpected and important results which have 

 aiisen out of these inquiries, will be deemed by you and the shareholders at 

 large, to be a sufficient apology for the delay which you have experienced in 

 not receiving this report at the time originally contemplated ; to comply 

 with which, to the utmost extent in my power, must also be my apology for 

 the imperfect manner in which this document is presented to your notice. 

 I am. Gentlemen, 



Your most obedient senant, 



NICHOLAS WOOD. 



REPORT OF I. K. BRUNEL, ESQ. 



TO THE DIRECTORS OF THE GREAT WESTERN RAILWAY COMPANV. 



Gentlemen, — I have now before me the report of Mr. Wood, the latter part 

 of which I received only on the 17th. The appendix, without which, for all 

 purposes of investigation, the report is incomplete, I have not j'et received. 



Considering the great mass of valuable matter contained in this report in 

 the shape o^ numerous experiments, of calculations founded upon them, and 

 the discussion and examination of the results and their consequences, the 

 collection and consideration of which have occupied several persons for about 

 three montlis, it will not surprise you that I should find a few days a very 

 short period in which to make myself sufficiently master of its contents to be 

 able to lay before you my observations thereon. 



The extremely short time which circumstances allow me will prevent my 

 entering into a detailed examination of the various tables of experiments which 

 appear in the body of the report, or, in fact, doing more than refer to the prin- 

 cipal points and those general results which appear to have mainly influenced 

 Mr. Wood's opinions. Fortunately, the clear and methodical manner in 

 which these various results are arranged, and the fair and impartial way in 

 which they are treated, will render this an easy and comparatively an agree- 

 able task,"and will enable me to select such points as I consider most impor- 

 tant, and to separate such facts and conclusions as relate to these particular 

 points. 



The satisfaction which I feel in approaching a subject, when treated in this 

 manner, is, however, very much diminished by one source of great regret ; 

 and if in the course of the following observations I should have occasion to 

 differ from Mr. Wood, either in the view he takes of the reliance to be placed 

 on, or the consequences resulting from, any particular experiment, I ascribe 

 this difference of opinion almost entirely to the cause which I shall refer to. 



I think it is deeply to be regretted that Mr. Wood should not have been 

 able himself to have attended to and conducted all the experiments. I do not 

 mean to imply the slightest doubt of the accuracy of the records of the facts 

 as they were observed ; but that constitutes but a small part of the duty of 

 collecting evidence upon doubtful points, particularly when they relate to 

 questions of mechanics and science, which may be affected by a great variety 

 of causes, and where the results may be influenced and entirely changed by 

 the manner in which they are obtained. 



It is certainly my opinion, that had Mr. Wood personally superintended the 

 experiments ; had he brought his own practical knowledge of the subject to 

 bear upon them ; he would have discovered many operating and interfering 

 causes, which either would have led him to repeat his experiments by other 

 methods, or to explain apparent anomalies, and thus, in my opinion, upon 

 many of tire most important points to come to very different conclusions. But 

 more especially do I think his opinions would have been changed upon all 

 those points which are necessarily capable of alteration and amendment by the 

 k-uowledge and experience daily gained in the working of a system new in 

 manv of its details ; and that before he drew definite conclusions, founded, 

 inevitably, upon very imperfect data, he would have made a larger allowance 

 for that progressive improvement which practice, observation, and experience, 

 never fail to produce. 



To no part of the system do these remarks apply more strongly than to 

 that of the performance of the locomotive engines, and the question of the 

 practicability of attaining high speeds ; and as almost the only conclusions 

 arrived at iu the report upon which I think it necessary to epxress any material 

 difference of opinion, are founded entirely upon the results of experiments made 

 to determine these points, I shall apply myself principally to the consideration 

 of them, and the experiments by whicli they were obtained. 



In order to show that I am not attaching undue importance to any one part 

 of the report, or to any one section of the experiments, I shall refer briefly 

 the general arrangement of the report, and to the order in which the con- 

 clusions are arrived at. 



After stating the general questions to be treated, and the advantages and 

 objections which have been urged for and against the plans which have been 

 adopted on this railway, Mr. Wood arranges under' three principal heads the 

 points to be determined by experiments, viz. : — 



" 1st. The question of the attainment of a higher rate of speed than on other 

 railways ; whether the increased width of gauge is, or is not, either 

 necessary or best adapted for the accomplishment of this object, and 

 to what extent. 

 "2nd. The mechanical advantage or diminution of friction, by being enabled 

 to increase the diameter of the wheels without raising the bodies of 

 the carriages; and in what respect, and to what extent, the friction or 

 resistance of the carriages is affected by, or bears upon, the peculiar 

 construction of the road. 

 "3rd. The comparative advantage or firmness of base, or road track, of the 

 Great Western Railway, with continuous timber bearings, either with 

 or without piles, and if it does or does not produce a greater steadiness 

 and smoothness of motion to the carriages, and to what extent. 

 " These were the questions," the report continues, " vvhich it appeared to me 

 could not be determined in any other way than by experiment, but which ap- 

 peared to be capable of solution by that method, and which likewise appeared 

 to constitute the foundation of the entire system." 



The first division consists of summaries of experiments, the details of 

 which are to be given in an appendix, and of observations upon the perform- 

 ance of the Great Western engines, as compared with those of other railways, 

 and the comparative performance of all at different velocities. These constitute 

 the first section, and occupy the report to page 63. From thence to page 65 

 of the report is devoted principally to some experiments made upon the 

 resistance of the air to the moving train, with a view to account for, and to 

 ascertain the eauses of, the results apparently obtained in the experiments 



