340 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[NOTEMBER, 



there is sufficient time between the stoppages for the express train to get a 

 considerable distance, not much would be saved on a single line. On a double 

 line it would be necessary to send express trains, and tbcy could overtake 

 and pass other trains," 



Pelerlorovgh and Xorthamplon Raihvaij. — Arrangements that are made 

 for working this line, being a single line with the exception of five miles ; 

 number of trains that might be run in the course of a day — (Slephenson.) 



" The proposed arrangements are simply these ; that an engine is to run 

 from Peterborough to Tbrapstone, and back again from Thrapstone to Peter- 

 borough. There will consequently be only one engine upon each section of 

 the railway at the same moment, therefore a collision is absolutely impossi- 

 ble. But in addition to that we propose erecting an electric telegraph, which 

 will convey intelligence from station to station as the train passes, and there- 

 fore the whole line will be informed of the progress made by the train ; and 

 consequently risk from collision, even supposing we worked the engines 

 through, is almost impossible. I conceive that, without the most gross and 

 wilful neglect on the part of the engine-men, it is impossible that any acci- 

 dent can happen. You might work eight trains a day each way, from North- 

 ampton to Peterborough. For a traffic of that kind you could safely recom- 

 mend a single line upon the locomotive principle ; but upon a much more 

 extensive traffic, you would not recommend a single line, even though the 

 atmospheric system were adopted? — No; but a single line upon the atmo- 

 spheric system would have cost as much as the locomotive line has cost ; for 

 the Peterborough line has not cost more than 7,000/. a mile for the engineer- 

 ing; therefore, taking Mr. Samuda's estimate of 6,000/. a mile, it would 

 make it ruinous, the traffic being small : wherever the trafSc is small, the 

 application of the atmospheric system must result in ruin to it ; it is inevit- 

 able. Can you give any estimate of the cost of a single locomotive line on 

 the same principle as Mr. Samuda has adopted in giving the cost of a single 

 line atmospheric, viz., assuming the country to be as level as a bowling- 

 green ? — I can ; I have taken the Yarmouth and Norwich line ; I happened 

 to have all the facts before me in detail ; the actual cost of that line, ex- 

 clusive of the land, which is common to both plans, is 150,000/. 



Phton. — It is proposed to have an expansive piston on the South Devon 

 line to accommodaie itself to the varied size of the tubes — (Samuda.) 



Power : 1. Production of Power under the two St/>;tems. — In an ordinary 

 train the power exerted to move the engine and tender bears a very large 

 proportion to the power to move the train with passengers ; explanation in 

 detail showing this fact — (Stephenson.) 



" I find that a locomotive engine will absorb nearly as much power as 

 about 15 loaded carriages ; so that the actual quantity of power expended 

 with an ordinary locomotive train of eight carriages ; say in point of power 

 (I am now speaking not of cost, but I am speaking upon the abstract ques- 

 tion of power), is equal to the expenditure of power upon 23 carriages ; and 

 I find that in the same proportion, take the engine, say at Camden Town, 

 the friction of the rope, and the loss by other circumstances, is very nearly 

 as much, except with light trains. Then the proportion, of course, as you 

 diminish the weight of the train, to the locomotive engine, becomes more 

 and more unfavourable to it, because the resistance of the engine itself still 

 remains constant ; if you have only one carriage behind it, it will be the 

 same as though you had IG, though there may be only one beneficially em- 

 ployed." 



Calculation showing that though there is more economy in the means of 

 raising power by a stationary engine, there is a greater deduction to be made 

 in consequence of the unemployed intervals ; instance of the Dalkcy line — 

 (Stephenson.) 



" On the atmospheric system it is cheaper to move a given number of pas- 

 sengers by a larger number of light trains than by a smaller number of heavy 

 trains. But when I refer to the question of power, and the expense of pro- 

 ducing that power, all my answers have reference to the time during which 

 the power is being produced ; that is, during the engine is in motion. A 

 stationary engine, under those circumstances, is very much more econo- 

 mically worked than a locomotive (that is, during a certain time, while pro- 

 ducing a given quantity of power) ; but in regard to all stationary power, the 

 loss of fuel, and the loss of money, in fact, during the time it is not in action, 

 is far more than equivalent to the disadvantage which the locomotive engine 

 labours under during its actual motion ; and consequently, practically, if you 

 take the question as applied to the whole day, the stationary system becomes 

 the most extravagant. At Dalkey, when I was there, there were 10 trains a 

 day running each way; the consumption of fuel then was upon the train 

 mileage 266 lb. a mile. I understand from the evidence given by Mr. Ni- 

 cholson, whose papers I had an opportunity of perusing, that the consumption 

 of fuel when 27 trains a day are running is 1151b. per mile per train, which 

 is less than one-half ; that is the consumption of fuel to useful efl'ect. On 

 the Blackwall, where the trains are three times the weight of the Dalkey, 

 and where they run bi trains a day each way, the consumption of fuel is 

 only 661b. per train per mile, which is one-half; therefore, comparing the 

 Dalkey as it was with 10 trains a day with the Blackwall with 5t trains a 

 day, the one is 2661b. per train per mile, while the other is 661b., being 

 fully four times as much per mile of useful effect." 



2. Application of Power on the Atmospheric and on the Locomotive Prin- 

 ciple. — On the atmospheric system the amount of power is always used which 

 is necessary for the work. The power can be adjusted to the load by pro- 

 ducing a greater or less vacuum, and consequently a greater or less pressure 

 upon every square inch of the piston — (.Samuda.) 



On the South Devon line it is intended that the engine next ahead of thta ' 



immediately in front of the train should he at work at the same time, and 

 that the force of both should operate upon the train — (Brunei.) 



3. Loss of Power in each Mode of Traction. — In the atmospheric svstem 

 the only loss of power, apart from imperfect machinery, arises from the at- 

 tenuated air in the tube being heated, and having to be compressed by the 

 air-pump, by which, however, the loss of power is not 10 per cent. Expe- 

 riments have been tried on the Dalkcy and Kingstown line to protect the 

 pipe from the external air, but no such plan would pay — (Brunei.) 



Resistance offered by the compression of the rarefied warm air in the air- 

 pump previous to its expidsion into the atmosphere ; this might be obviated 

 — (Robinson.) 



" The only difficulty which, theoretically speaking, occurred to any one 

 who thought on the subject, but of which no one had anticipated the full 

 effect, was this, that during the expulsive strokes of the air-pump, that is, 

 when the air that has been drawn from the main is expelled into the atmo- 

 sphere, a considerable quantity of heat is evolved by the condensation of the 

 rarefied air; the amount of this far surpasses what I at least had anticipated 

 from the existing theories. It increases the elasticity of the air so condensed, 

 and, therefore, increases, beyond what theory would assign, the resistance 

 to the motion of the air piston. Do you contemplate that anything might 

 be done to abate that loss of power by the heat evolved in the condensation 

 of the air ? — Unquestionably; modes of exhausting can easily be conceived 

 which would be free from that. Vvill you state what those modes ai-e.' — I 

 am, perhajis, scarcely at liberty to do so, because I derived the idea from the 

 researches of a friend who is engaged upon the subject ; 1 will name the gen- 

 tleman, the secretary of the Dublin and Kingstown liailway, Mr. Bergin; he 

 showed me the results of his experiments ; I therefore do not feel at liberty 

 to mention them. I consider that thej are likely to be attended with suc- 

 cess." 



Deductions to be made from the power of the atmospheric engine; first, 

 on account of the force required to draw the air through the pipe ; and, se- 

 condly, for the friction of all the valve apparatus — (Robimon.) 



" The French engineer, i\I. Mallet, who came over to make experiments, 

 in his report has given the result of the different experiments which he made 

 with the piston carriage ; it was at a velocity of 20 miles an hour; he de- 

 duces, that he required, to overcome this friction, and also to lift up the 

 valve and seal it again, a force amounting to a total of 35 lb. ; that is so 

 small that I did not reduce it to horse power. And I must add to that 

 another, the evidence of which has been established by experiment ; one may 

 say in general, the atmospheric system is like drawing by a rope which has 

 no weight, which is perfectly elastic and is capable of transmitting almost an 

 infinite velocity ; but the velocity has a certain limitation. It requires a 

 little force when you begin to exhaust the tube to draw the air through it to 

 the pump. In some experiments that were made for the purpose, holding 

 the train by the break, working the engine and having two chronometers 

 carefully compared, looking at the gauges at the ends of the line, and noting 

 at each successive series of 15 seconds the height of the gauge, you got a 

 comparison of the difference of the two gauges, which is the pressure at the 

 two ends of the line, and then the train was allowed to start, and the baro- 

 meter was still observed. Y'ou cannot observe, with that precision, the height 

 of the barometer in the piston carriage, because it goes up and down so 

 much ; but still, as far as it could be ascertained, there appeared to he the 

 same difference of about three-quarters of an inch of mercury ; an inch of 

 mercury is half a pound ; that will be three-eighths of a pound, which was 

 the force required to purop the air through the pipe to the air-pump ; then 

 take that three-eighths, and then allow for the friction of the piston, which 

 will be little more than another eighth, and you will have the pressure on 

 the mercury, that v\ill be half a pound on the square inch of the tube's dia- 

 meter, for the friction of the piston apparatus, and the force required to open 

 the valve, and the friction of the air." 



Different kinds of power available for railway purposes are the stationary 

 engine with ropes, applicable to flat or hilly countries ; the locomotive sys- 

 tem ; and, third y, the atmospheric. Loss of power under these different 

 systems ; in the first case the friction of the rope ; in the locomotive the 

 weight of the engine when moving from a level, and the resistance of the 

 air ; and in the atmospheric the leakage. Witness made an experiment by 

 which be found that the quantity of power lost by the friction of the rope 

 in the case of the Euston plane, from Euston-square to Camdeu Town, was 

 as nearly as possible equivalent to the loss on the Dalkey line by leakage. 

 The waste of power on the locomotive and on the atmospheric systems is 

 pretty much the same. On the atmospheric plan there is a loss of power in 

 getting up the vacuum in the tube ; on the Dalkey line this is almost en- 

 tirely lost; this is a loss of the same kind as getting up the steam in the 

 locomotive engines, but not to the same extent — (Steplienson.) 



" It has been stated that with a vacuum of from 18 to 20, from 60 to 70 

 percent, of the power generated by the steam-engine is wasted.' — I must 

 say that at present I am not in a position to believe that ; I do not think it 

 is so" — (Cubitt.) 



Ralls and Slecfierg.^On the atmospheric plan the rails and sleepers may 

 he lighter than in the locomotive lines — (Samuda.) 



On the Great Western railway the rails are 7011). per yard; on the South 

 Devon, 50 lb.; the latter will probably last the longest — (Brunei.) 



Less deflexion would take place on the rails of an atmospheric line, even 

 if they were considerably lighter; a 501b. rail would be much stronger than 

 a 70 lb. rail on a locomotive line — (Robinson.) 



The engines used on the Dublin and Kingstown railway are ss heavy as 



