1847.]- 



THE CIVIL ENGINEEERAND ARCHITECTS JOURNAL. 



45 



occasioned on stoppins at tbe termini, by coming into contact either with 

 the walls or the carriages. This occurs either from the ignorance or neg- 

 li"-ence of the engineers, and sometimes from a derangement of the brake 

 not allowing the train to be stopped with sufficient promptitude. 



In ordertoobviate this, it would be advisable to direct the engine-drivers 

 to stop the train completely before reaching the place where the passengers 

 are to alight. When a train is in progress, it is indispensably necessary 

 for the engine-driver to be constantly warned of all that passes on the 

 line ■ and for this purpose there must always be, between the engine drirer 

 and station-guards, certain signals, which may be readily understood by 

 the latter ■ and by means of which the station-keepers may always com- 

 municate with each other. Signals between the engine-driver and guard 

 of railway trains either do not, for the most part, exist, or are very imper- 

 fect It will nevertheless, be readily conceived, that many casualties may 

 arise durin"- the progress of a train, of which it is necessary for the engine- 

 driver to ha°ve notice,— as in case of the breaking of an axle, the carnages 

 Fanning off the rails, &c. The Commission thinks that Government ought 

 to direct that in each passenger-train there should be a guard, furnished 

 with the'means of communicating the necessary intelligence to the engine- 



driver 



Another subject of great importance in railway transit is the question,— 

 at what speed they should travel > and on this head, the Commission de- 

 liberated, first, whether it would be advisable to fix a maximum speed ; 

 but it was found, that a speed which would be without danger on very 

 fdight inclines and curves of large radius, would be extremely dangerous 

 on steep inclines and curves of small radius, and which were to be tra- 

 versed by heavy trains ; it is, therefore, proposed to fix a maximum speed 

 for each road, regard being had to the inclines and curves on each line, 

 and also to the trains to run upon it. 



It would also be very useful for each engine to be furnished with an 

 apparatus for indicating (permanently and independently of the will of the 

 engineer) the maximum speed of the train at any period of its journey. 



Ncte on Experiments made upon the new line qf rail at Saint Gennain, 

 with, a Locomotive constructed by M. Flachat. 



The town of Saint Germain is situate on an elevation of abont sixty 

 yards above the plain upon which the line of rail terminates at the Pecq 

 iirid^e The atmospheric railway overcomes this diSereuce of level by 

 mean's 'of a series of gradients, forming altogether a parabolic curve, 

 sloping towards the earth, and terminating in a gradient of 10S3 yards in 

 length, and having an inclination of 35 yards. _ 



M Flachat.who was charged with the superintendence of the works, 

 acknowledged the necessity of constructing a powerful engine, capable of 

 propelling upon steep inclines the materials necessary for the construction 

 of the road, and the apparatus for the atmospheric plan. The engine is 

 now employed for drawing earth from cuttings in the forest of Saint Ger- 

 main • the wagons running up empty, and returning full. 



The experiment made on the nth of June last, was for the purpose of 

 ascertaining the maximum weight the engine was capable of drawing on 

 the above i'ncline. The train consisted of four wagons loaded with earth, 

 and weighing, when empty, between three and four tons. One wagon was 

 found, vvhen loaded with earth, to weigh neaily 12 tons. The load, on 

 descending, was therefore — 



The Engine, weighing about 20 tons. 



TheTender 9 •• 



Four loaded Wagons , '* 



A Brake Carriage ^ ■ ■ 



76 tons. 

 The train started at a moderate speed, with the regulator entirely closed. 

 The train having once stopped, it was found to be impossible to ascend 

 again. One, two, and three wagons were then successively emptied, and 

 ii was not possible to ascend the incline until this was done. The ti-ain 

 therefore consisted of — 



The Engine ^J t°°^ ) 29 tons dead weigkt. 



TheTender 9 .. J 



Three empty Wagons .. .. 9 .. ] 



A loaded Wagon It .. 1- 23 tons useful weight. 



A Bralie Carriage 8 .. J 



This experiment was made twice, and gave the same results both times. 



The engine was working at a pressure of five atmospheres; the power 

 it exerted" supposing the action of tlie steam to be the same throughout, 

 was therefore about 3 tons 4i cwt. The resistance to be overcome was as 



follows ! 



tons. cwt. Ih. 

 Friction of various kinds, reckoned as 200th of the weight (71! tons) 7 5ft 



Action of gravity .. - '" 



2 3 66 



There remains a difference of 1 ton, IJ cwt., owing to the diminution of 

 pressnre, and additional friction of all kinds, and other casualties. It will, 

 of course, be understood, that on less steep inclines this tractive power 

 will be much increased. 



REVIEWS. 



The High Pressure Steam Engine investigated : an exposition of ill com- 

 parative merits, and an essay towards its imj}roved construction. By Dr. 

 Ernst Alban, practical machine maker, Plan, Saxony. Translated by 

 \V. Pole, F.R.A.S. Parts I. and 11. Weale, 1817. 8vo., pp. 145. Six 

 plates. 



The object of this book is a novel one. It is to advocate the superiority 

 of the high. pressure over the low-pressure engine ; and the omission of all 

 exceptions in favour of the latter kind of engine leads to the inference, that 

 the author recommends the adoption of the former under all circumstances, 

 and for all purposes. 



Dr. Alban tells us that be is a practical manufacturer of engines ; that he 

 has been engaged for thirty years, without intermission, in studying this 

 subject ; that he has made a large number of engines of various dimensions 

 and varieties ; and has been in the constant practice of experimenting with a 

 view to their improvement. A man who brings forward hie opinions thu? 

 authenticated by long experience, has a right to demand some attention to 

 them, and will generally have something to say which is worth listening to. 

 This is the case in the present instance ; but while full credit is to be given 

 to our author for his practical knowledge, it must be premised that he has 

 confined his attention almost exclusively to engines worked by high pressure, 

 and consequently is far more qualified to speak respecting their advantages 

 and capabilities than respecting those of low-pressure engines. Possibly, had 

 he studied the latter more, he would have thought better of them. 



These considerations apply exclusively to Dr. Alban's practical knowledge 

 —his theoretical opinions are to be criticised independently and abstractedly. 

 We shall find that his physical conceptions, though often clear and vigorous, 

 occasionally lead him into serious errors. The translator of this work sets 

 out with high professions of the necessity of theoretical accuracy, and laments 

 the aberrations of the unlearned in a manner which to some of his readers 

 will appear amusing. He is very caustic respecting the unhappy frequency 

 of blunders arising " from the practical methods adopted by ignorant men," 

 and complains that " unhappily, in most cases, the unfortunate public have 

 to pay for the schooling of their engineer,"—" unless the engineer has a 

 knowledge of principles to guide him, and a capability too of reasoning on 

 those principles." After this wholesale condemnation of engineers, it might 

 have been hoped that Mr. Pole would have at least avoided the errors which 

 he denounces, and that he would not have published in an English form 

 several notions greviously at variance with the said " knowledge of princi- 

 ples." Ke professes to correct his author's mistakes, but the worst of them 

 are passed over uncorrected, and apparently unobserved. 



Of the two Parts of the work before us, the first is theoretical ; the second 

 refers to details of construction. We shall for the present confine our at- 

 tention to the former, in which the author examines the objections brought 

 against high-pressure engines, and replies to them, and then proceeds to a 

 serial account of the advantages peculiar to these engines. 



The objections may he considered first— they are principally these five. 

 1st. The danger of explosion: 2nd. The loss of heat : 3rd. The rehnquisb- 

 ment of that power which arises from condensation: -ith. The consumption 

 of oil and grease for lubrication : 5th. The wear and tear of metal from the 

 rapidity of motion. We will take these objections in their order. 



The first oijection— respecting the danger of explosion— may he considered 

 to be of a two-fold nature: for we have to ascertain primarily whether a 

 high-pressure boiler be more likely to explode than a low-pressure boiter ; 

 secondarily, whether the results of an explosion are more disastrous in the 

 former case than in the latter. Our author does not make this distinction ; 

 but it is obviously necessary for the complete esammation of the subject. 

 In comparing the probabilities of an explosion occurring in either case, we 

 must, of course, for the fairness of comparison, pre-suppose that, ceteris pari- 

 bus, the metal of the boiler is always made of a thickness proportional to 

 the intended steam pressure : that is, that a boiler intended to bear a ptes- 

 Bure of four atmospheres, is made twice as strong as one intended for a pres- 

 sure of two atmospheres, &c. Unless this supposition be made, an accurate 

 general comparison of the probabOities of explosion would be impossible : 

 and, moreover, the precaution is one so palpably necessary, that no man of 

 common prudence would neglect it. This being premised, we proceed to 

 our author's first view of the case. 



" Every boiler may become supercharged with steam when the quantify 

 drawn off is less than the quantity generated, and when the safety-valves, in 



