Gft 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



to yniu' nolicp ; at the same tiinc, I beg to mtd, that I liiiTf in the slioit 

 perioil allowed to me, availed myself of every fact or ilisoovery of a practical 

 nature, wliicli appeared to me to hear upon the question, or to he in any way 

 conilucive towards your interests. I have, in the appendix, fjivcn in detail 

 all the experiments which I thouRhl would he of any utility, and from which, 

 aX any suhseiiuent period, the valualile information contaimd therein may he 

 extracted and investigated ; and it occurred to me to lie very important that 

 the^e documents should he (;iven in such a manner and in sncli detail, that it 

 should he in the power of yourselves or your engineer at any time, to exa- 

 mine into and compare the conclusions which I have arrived at, and which 

 appear to me to result from these experiments, with the experiments and 

 investigations themselves. 



Widlb of Gauge. — Pursuing the same arrangement as set out with in the 

 first part of this report, I shall now consider in what manner, and to what 

 «'xtpnt, the results of these investigations and experiments hear upon the rea- 

 sons which induced the adoption of the increased width of gauge, and the 

 particular construction of the Great Western Railway. 



The tirsi is the attainment of a high rate of speed. The experiments on the 

 power of the locomotive engines show, that the engines at present employeil 

 on the London and Birmingham Railway accomplish an average rate of 

 speed of 32 miles an hour, with weights equal to that of a first-class train, 

 (Tahle III.); hut that engines in the proportion of '263] 16o, more power- 

 ful than these, are in existence on the same width of railway. The 

 less powerful engines accomplish a rate of speed within three miles an hour 

 of the most powerful engines on the Great Western Railway, (Tahle V.); 

 and, therefore, the presumption is, that if the more powerful engines on the 

 ordinary railways had been tried, they would have accomplished a higher 

 average rate of speed than the most powerful engines on the Great Western 

 Railway, the effective power apparently yielded hy the former being nmch 

 greater tlian the latter. But we now find that a cause exists which perfectly 

 accounts for this comparative diminution ofefl'ect, and that it is, in fact, if not 

 almost entirely, attributable to the greater atmospheric frontage of the Great 

 Western Railway carriages, than those upon the London and Binuingham 

 Railway, and the powerful effect which the atmosphere has upon the resistance 

 to he overcome. 



The experiments on atmospheric resistance being as yet confined to the 

 carriages of the narrow gauge, we cannot satisfactorily determine what the 

 precise increase of resistance will be by an enlarged frontage ; the carriages 

 of the Great Western Railway are 10 feet higli from the rails, and !) feet 

 wide ^90 square feet, whereas the London and Birmingham Railway car- 

 riages are only 9 feet high and Of feetwide = IJO square feet; hut an open 

 space exists below the wheels, which is only partly filled up by the fire-box 

 of the engine ; taking, in each case, a foot from the rails to he clear space, 

 the relative area of frontage will be 81 : .53. Every circumstance being the 

 same, we may suppose that the atmospheric resistance will he as the area of 

 frontage, but the figure of the engine preceding- the carnages, the comparative 

 length of the train, and several other circumstances, may affect the result ; 

 and, therefore, until the question has been satisfactorily determined by ex- 

 periment, no comparative standard can be assigned of the relative amount of 

 atmospheric resistance to trains of different areas of frontage. 



For these reasons, therefore, I shall not go into an analysis of the pre- 

 sumed resistance of the Great Western trains, as compared with those of the 

 London and Birmingham Railway ; for the same reasons, likewise, it will at 

 once appear to be impracticable, with the data «e are at present in posses- 

 sion of, to determine with any degree of acciu-acy the comparative adi'antage 

 of large and smaller driving wheels to the engines ; — the incontrovertible 

 conclusion, that a very large proportion indeed of the resistance of railway 

 trains is attributable to atmospherical resistance, is quite sufficient to account 

 for all the differences of results between the engines on the two descriptions 

 of railways ; but to w hat extent, and what portion is attributable to atmos- 

 pherical resistance, what part to the engines, and what portion to the car- 

 riages, varying as both engines and carriages do, in the diameter of their 

 wheels, cannot be conclusively determined at present. 



There ?\m he little doubt that the atmospherical resistance varies at least in 

 the ratio ^ f the square of the velocity ; considering, therefore, this rapid 

 increase of resistance, it appears to me, that no other conclusion can result 

 from these experiments, than that it is not advisable to attempt an extreme 

 rate of speed, and that 35 miles an hour, with the existing engine powers, may 

 he considei'ed as the limit of practical speed for passenger trains; combining 

 economy with regularity of transit, and giving due weight to the necessity of 

 accommodating the public, as regards celerity of travelling, to the utmost 

 practicable extent. 



If such a conclusion is warranted by these investigations and experiments, 

 then it results that it is not necessaiy for the attainment of such a rate of 

 speed, that the gauge should he seven feet. 



The next proposition is the mechanical advantage of increasing the diame- 

 ter of the wheels, without raising the bodies of the carriages. We see that 

 there is a diminution of friction bv the increase of the diameter of the wheels, 

 but it is doubtful to what extent this is modified by elevating the bodies of the 

 carriages ; a broad gauge by allowing the bodies of the carriages to he placed 

 within the wheels, and thus to reduce the height of the carriages, and conse- 

 quently diminish the area of frontage, is an advantage, considering the great 

 amount of resistance arising from the atmosphere. Then to carry out the 

 premises fully in this respect, we must not give any greater width of frontage 

 than is absolutely necessary for that purpose ; it will dejiend upon the result 

 of further inquiries, as to what superficies in terms of length and width of train 

 affords the requisite accommodation, and presents the least resistance to the 

 atmosphere, which has not been yet determined. 

 The next proposition, that the iucreased width of gauge admits all sorts of 



carriages, stage coaches, &c., to be carried within the wheels, is readily an- 

 swered ; any width of gauge which reduces the height of these carriages above 

 the rails, will be preferable to that width which does not admit of such an 

 arrangement; and the ordinary width, not admitting them within the wheels, 

 renders an increased width, in this respect, advisable, this can, however, he 

 cfl'ected with a less width than seven feet. t 



Increased facilities for the adoption cf larger and more powerful engines, 

 for the attainment of a higher rate of sjieed, has been answered previously; 

 it not appearing necessary for such a purpose that the w idth should be seven 

 feet. The remaining proposition is, that a wider gauge affords increased 

 stability to the carriages, and, consequently, increased steadiness of motion. 

 The diagrams given will shew how far this has been eflected on the present 

 portion of the Great Western Railway, aud certainly these documents would 

 prove that this has not yet been accomplished. Considering, howe^'er, the 

 causes of the dili'erent motions of railway carriages, there can be no donbt, 

 that an increased width of gauge must tend to produce that effect. In the 

 present instance this has been counteracted by the consti'uction and present 

 condition of the road and carriages ; and therefore it appears to me the only 

 conclusion we can come to is, that in similarly constructed railways the wider 

 gauge will afford greater stability and steadiness of motion to the carriages. 



The objections alleged against the increased width, as detailed in page 8 of 

 this report, no doubt exist to a certain extent : the expense of forming the 

 road track of the railway is increased. This Mr. Brunei estimates at 151,840/. 

 for the entire line. The carriages are larger and heavier, and so far, there- 

 fore, as the weight acting upon the rails may he objectionable, must he ad- 

 mitted ; but I find that Mr. Brunei's statement of the relative weight,per pas- 

 senger, given in his report at the last meeting of the shareholders (vide Jciu"- 

 nal No. 12, page 324, vol. 1), confirmed by my enquiries, which shows that 

 there does not exist a greater weight, per passenger, with the Great Western 

 than with other carriages. 



The increase of friction in passing the curves does not apply with much 

 weight in your case, the radius of these being so great. The comparative 

 expense of construction of the engines and carriages are not matters of great 

 moment, as there would not be any material diflerence if the engines were 

 similarly constructed ; and the amount, per passenger, is nearly the same 

 with the carriages. The next objection, that it prevents a junction with 

 other lines, does not .npply with such force to the Great Western Railway, as 

 it would to some other lines; that railway being complete of itself between 

 the two sides of the island. How far this may be affected by the branches, I 

 am not capable of judging, it being more a commercial than an engineering 

 question ; and an opinion could only be satisfactorily given, by an intimate 

 aciiuaintance with all the circumstances attending the required connuunicatiou 

 with the adjacent country. 



The last objection, that there are no advantages gained commensurate with 

 the increased expense and inconvenience of such a departure, and connection 

 from railways of the ordinary width, does appear from a full consideration to 

 he substantially confirmed ; at the same time I must be allowed to say, that 

 there are counteracting advantages, incidental to an increased width of gauge, 

 above that of oli inches, which should not he overlooked. 



Almost all the results arising from these enquiries go to establish a conclu- 

 sion, that 7 feet is beyond that width which may be considered the best; but 

 these investigations are far from conclusive, in the present state of our infor- 

 mation, as to what other width is, under all circumstances, the most advisable 

 to be adopted. Under these circumstances, and considering the great sacri- 

 fice of property which would result by the removal of the present rails, and 

 the substitution of any other width ; it appears to me that such a step would 

 not be justified by the result of these enquiries. We have only determined 

 one part of the proposition, viz., that seven feet is too great a width ; we have 

 not determined the most important section, to what injurious extent it will 

 operate practically. The only results bearing upon this is the increased 

 power required by the enlarged width, aud that is in some respects shewn by 

 the increased consumption of coke ; which, as per table V., appears to be with 

 the North Star, 21 jibs, per mile, and with the iEolus, 8Jlbs. per mile addi- 

 tional, the former, however, effecting an increased rate of speed of two miles 

 an hour. It is also necessary to state, that the results elicited in the course 

 of this enquiry shew, that considerable modifications may be beneficially 

 made in both engines and carriages ; and, therefore, until we have determined, 

 in the most satisfactory and conclusive maimer, the precise extent of injury 

 arising from the retention of the present width of gauge, and what width best 

 efl'ects all the objects required, and which, under all the circumstances, is most 

 conducive to the interests of the company, and affords the greatest accommo- 

 dation to the public, it appears to me the present width should be retained. 



Construction of the llimd.- — The question of the construction of the road 

 comes next under consideration, and here, I presume, there will be less diffi- 

 culty than in determining on the width of gauge. No doubt can exist, after 

 these experiments, that the piles do not contribute to the firmness of base of 

 the railway, their action seems to prevent the contact of the timbers with the 

 ground ; and it is unquestionably proved, that the passage of the engines and 

 carriages along the rails, contributes, with a more powerful eflPect, to consoli- 

 date the road, aud produce a greater firmness of bearing to the rails, than the 

 packing connected with tlie jnles. 



The principle of having at the end of every lo feet, vis:, at the transoms, a 

 comparatively unyielding hearing, with a scantling of timber intervening, 

 very far short of the requisite strength to support the weight of the engine 

 ami trains, renders it extremely difficult, if not impossible, to produce a 

 uniform rigidity of surface throughout ; and this uniformity cannot be 

 effected by any system of packing, dependent upon manual labour. If con- 

 tinuous bearings are preferable to isolated supports, it appears to me that the 

 most economical, and most perfect plau of couatructiou of continuous timber 



