198 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[June, 



carried annually from one extremity of the line to the other be known." 

 Now, hitherto we have been unable to determine a priori what these amounts 

 are — but we can tell w ith great accuracy what they have been on the differeiit 

 Bncs of railway now in operation. The following tables give the average of 

 these expenses on several lines of railway : — 



Merchandise Traffic. 



Coal on colliery Goods on the 

 Heails of charge. railways in the Liverpool and 



north. Manch. Rlny. 



Locomotive power — wages and repairs . . . . OSSS" . . . . 425* 

 fuel 0025 .... 0125 



Total 0-380 0-550 



Wagons 0-190 .. .. 0227 



Conducting traffic 075 .... 1080 



Maintaining railway 0-208 .... 0-307 



General expenses 0-100 .... 0354 



Total cost 0-953 2-518 



* Per ton per mile — in decimals of a penny. 



Passenger Traffic 



Lend. U Mane. Dublin & Kings- 

 Heads of charge. Railw. — average townRailw. — av. 

 60 passengers 40 passengers 

 per train. per train. 



Locomotive power — wages and repairs .. 0'170* 0-173* 



fuel 0100 0-115 



Total 0>270 



Coaches 0-054 



Conducting coaching 0104 



Maintaining railway 0-085 



General expenses 0-091 



0-288 

 0-031 

 0-113 

 0-050 

 0-174 



Total cost 0-604 0-656 



* Per passenger per mile — in decimals of a penny. 



Taking the Liverpool and Manchester Railway as an example, we find the 

 uiunber of passengers to average sixty per train. This may, on the whole, 

 be considered as a fair average on all the railroads throughout the country. 

 Seven years working of the same railway gives, as the average expense of 

 locomotive power, 0-27<i. or about \d. per passenger per mile. The gradients 

 do not exceed six or seven feet per mile, with the exception of the inclined 

 plane, and this also is an average amount for most railways— in fact, fuel 

 and wages are so nearly the same on all lines, that the expense of this bead 

 can be calculated with great exactness. The expense of locomotive power, 

 also, is the only one which depends upon the gradients. The other expenses, 

 w-hich are independent of the gradients, are — coaching, conducting ditto, 

 maintaining way, and general expenses, altugethei- amounting to 0-33(i., which 

 ^ded to ^)^2^d. = 0-60<Z., or, in round numbers, three-fifths of a penny per 

 passenger per mile for the expense of transport. Now, let us examine the 

 relative expense of the merchandize traffic. We have, for the expense of 

 locomotive power, 0-55d., or, in round numbers, \il. per ton per mile ; for the 

 cost of wagons and secondary expenses, l-97(i., which, added to 0-55t/., gives 

 2-52d., or, in round numbers, 2\d. per ton per mile as the actual cost of trans- 

 port. Now, let us mark the very striking result of this comparison. Even 

 with all the most recent improvements, and cutting down every expense that 

 can be reduced, tbe mere transport of passengers costs three-fifths of a penny 

 per passenger per mile, whilst that of goods is only 2Jrf. per ton for the same 

 distance, and of tiiis Irf. may be thrown out, arising from other sources, 

 leaving the cost of transport — passengers, three fifths of a penny per passen- 

 ger per mile ; goods, Ijrf. per ton per mile. In the first case, we have an 

 amount exceedingly high, in proportion to the present means of transport, 

 whijst the second case presents a result as strikingly low. A ton of goods 

 is equivalent to the weight of foiurteen passengers, with 30 lbs. of luggage 

 eadi. 



When the loads to be carried are light, and the velocities at which they 

 are carried considerable, the steepness of the gradients is a matter of com- 

 paratively little consequence, but as soon as the engine is loaded to its maxi- 

 mum power, the railway system becomes unable to compete with the canals^ 

 S(j.fajr,as relates to the carriage of goods. If these are the results offered to 

 y«u by j^st experience, do jounot'see alt once ho-w it affects the (luestion of 



laying out lines in remote districts, where but a small amount of traffic can 

 be calculated upon? Again, referring to the table, with reference to the 

 difference between carrying slowly and carrying quickly, we find that the 

 expense of locomotive power on the Liverpool and Manchester Railway is 

 0-55rf., or nearly three-fifths of a penny, yet that the expense upon the best 

 railways, where goods are carried at a moderate velocity, is only 0-38fi. and 

 the remaining expenses 0-57rf., so that it comes to this, that we have — Liver- 

 pool and Manchester Railway, '2\d. per ton per mile; other railways, with 

 moderate speeds, \d. per ton per mile. M. Navier proposes a case not quite 

 so strong, perhaps, as might be made out, and I will, therefore, refer to the 

 Brighton Railroad for an example, the expense of which, for the 40 miles, has 

 been about £2,600,000, or £00,000 per mile, the interest of which, ;it 6 per 

 cent., is 10/. per mile per day, which is the net receipt, after all expenses are 

 paid, requisite to insure a decent interest to the shareholders. I shall not 

 enter further into the question now-, but if those students who are sufficiently 

 advanced will take up the subject, they will soon be able to appreciate my 

 arguments for increasing the limits within which gradients are usually kept 

 —for, supposing the expense of carrying a passenger should be only 'id. per 

 mile, yet, if you will calculate the additional expense of the interest of 

 £60.000 per mile, you will find ruinous results. 



M. Navier having said that the cost of transport is the chief point to be 

 attended to in laying out a railway, goes on to determine the amount of 

 power requisite to draw a given train over a given railway. The elder students 

 will, in connection with this subject, be aware of the opinion which has been 

 pretty generally entertained amongst engineers, that a rise of twenty feet pet 

 mile is equivalent to a mile in length. M. Navier says—" Let us observe that, 

 upon a horizontal line, the power required to draw a given weight is con- 

 sidered as being equal to almost the two-hundredth part of this weight;" but, 

 as I have shown in a previous lecture, the formula fur the expression of this 



F 



power will be ~ taking F as the friction per ton, and n the number of pounds 



in each ton, so that what M. Navier calls the two-hundredth part of the 

 weight » ill be friction divided by the number of pounds in a ton. Taking the 

 friction at 9 1b., we have ^j4!_ = ,5ii- nearly. At 11 lb., ^,0^=.:^; .and 

 I must here repeat what I have so often before stated to you, that, although 

 experiments have been made, which give so low a friction as 4 lb. per ton, 

 that, on an average, M. Navier is nearly right, when we take into considera- 

 tion the numerous causes of friction. M. Navier considers the power required 

 to draw a given weight " to be independent of the absolute velocity of 

 transit, although there is reason to believe that the tractive power increases 

 with the velocity." Now, it has been said that the friction is the same at 

 all velocities. I cannot fully concur in this opinion. I think the axletree 

 friction may be constant under all velocities, but that, from other causes, 

 there appears to be, 1 will not call it an increase of friction, but an increase 

 of resistance, the amount of w hich has not been satisfactorily determined. 

 M. Navier goes on — " We conclude from this, that, in order to transport, 

 with any velocity whatever, constant or variable, a weight, W, to a distance 

 represented by a on a horizontal line, it is necessary to employ the power re- 

 presented by y X a — that is to say, the power necessary to raise the weight 

 to the height " ■" or, in other words to transport a weight any given dis- 

 tance on a horizontal line, is equivalent to raising it the two-hundredth part 

 of that distance in vertical height ; and, although this is not quite coi-rect, it 

 is sufficiently so for general purposes. We have before assumed that it is 

 the same thing to go a mile round as to go over a hill rising twenty feet in 

 a mile. Now, a mile being 1760 yards, or 5280 feet, we have ^^ x 5280 as 

 the power required, which is equal to raising the weight 26 ft. But as the 

 friction varies, I think we have sufficient experience now to say it is about the 

 same thing to rise 30 ft. in a mile as tu go a mile round : but this is quite 

 independent of the question, whether you should or should not allow on one 

 hand, and deduct on the other, when the slope exceeds the angle of repose. 

 I have explained to you, on previous occasions, the difference of opinion 

 that exists on this point. Both Mr. Barlow and M. Navier allow the ad- 

 vantage up to a certain point, which they fix at about 1 in 180, beyond which 

 point they consider the whole advantage gained to be destroyed by the 

 necessity of putting on the break. Now, in practice, we do not find this to 

 be the case, until we come to 1 in 80, or thereabouts ; however, we may take, 

 as a general rule, M. Navier 's concluding words on this subject : — " The 

 length of the line remaining the same, the amount of power consumed to 

 effect the transit depends entirely upon the length of the line, and the dif- 

 ference of the level of its extreme points." The practical result which I 

 have endeavoured to lay before you this evening is, that the cost of transport 

 is the cost of the power combined with the interest of the original cost of the 

 line, and that the calculation of this combined expense must form the 

 element of comparison between different lines of raihvay. 



