342 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[November, 



Ye!>, Init the rnpc at Euston-sfiuare is peculiar, it is not a single rnpp, but an 

 endless rope; theiefore it is 2 miles of rnpe as compared with 1 J mile of 

 pipe. What is ihe utmost speed you have known to he attained upon a lo- 

 comotive line ? I have not myself gone more than 55 miles an hour ; that 

 1 have done upon the Great Western and the Northern and Eastern. Upon 

 the Great Western I have gone 53 and 55 miles an hour several times, he- 

 tween Bath and rSristol. In all the experiments I made upon the Dalkey 

 line with very light loads, a greater speed was attained upon that plane than 

 could have heen attainpil hy a locomotive engine; but with heavy trains a 

 locomotive engine would have heaten the atmospherin upon that identical 

 plane. What kind of weight do you mean liy heavy trains .'—The trains I 

 made experiments with were from'27 tons to 64 ; there was one of 70 tons. 

 And you think, with trains of thnt nature, a greater speed would he attained 

 hy the locomotive engines?— Up that gradient of 1 in 115, most decidedly, 

 because then the atmospheric leakage begins to tell, a train of Gl tons re- 

 quiring a vacuum of something like about 22 or 24 inches: whenever the 

 vacuum gets to that height, the loss of power by leakage is so great, and the 

 velocity so nuuh diminished, that the locomotive engine exceeds the atmo- 

 spheiic in speed most cnnsideraldy. 1 have here a table of the trains which 

 1 tried, varying them 2" tons. With light trains, the locomotive would have 

 heen at fault ; but with heavy trains, it would have been better than the 

 stmosphfric. 



It is quite possible to go from London to Exeter as fast by the atmospheric 

 as hy the locomotive principle. Higher velocities can be acquired and main- 

 tained on the atmospheric than on the locomotive system— (C«J//A) 



Judging from the reports and from the opinions of those in favour of the 

 atmospheric system, there is no reason to suppose that it has any advantage 

 over the locomotive with regard to the rate of speed— (iocic.) 



Facility of allainiwj a high Rate of Speeil, anil aim an Increase of Speed, 

 S(c. — Result of experiments as to the speed attainable upon an atmospheric 

 Jine ; the velocity can he determined upon with accuracy— (Z?«y/(;j,) 

 _ " Have you made any exper'ments as to the speed attainable upon an at- 

 mospheric line ? — I have ; I noted a consiilfrahle nuniher of trains with great 

 accuracy, and I have selected a few for the purpose of mentioning them to 

 the committee. On the 18th of November 1813, I noted a train which con. 

 sisted of six passenger-coaches, which were all well tilled, being something 

 like 30 tons gross weight ; the first quarter of a mile was passed in 44 se- 

 eonds; the second quarter in 29 seconds; the third in 28} seconds ; the 

 fourth in 28j seconds, and the fifth in 22J seconds. During this journey 

 Hie greatest speed attained was 45 miles per hour; I may perhaps add that 

 that weiglit of 30 tons gross, on that inclination, was equivalent to a load of 

 87 tons on a level. Again, oi. the 21st of November 1843, (Mr. Brunei was 

 present at the time,) I noted tlie time of a train consisting of 12 coaches and 

 wagojis full of passengers and loaded with iron, the total weight of which 

 was 71 tons 19 cwt., bring equivalent to 208 tons on a level ; the time occu- 

 pied by that train in traversing the first quarter of a mile was 88| seconds, 

 in tra\ersing tl:e second quarter of a mile was 49^ seconds; the third quarter 

 of a mile 47^- seconds ; the fourth quarter of a mile 50| seconds ; the fifth 

 qu-.rier of a mile 4SJ seconds, and the greatest speed attained was 20 miles 

 per hour up an inclination of 1 in 129. What was the amount of vacuum .' 

 I h;n-e not the record of that ; Mr. Brunei, I believe, took it ; 1 took these 

 speeds for Mr. Brunei, or in company with him, while he noted the vacuum, 

 and I neglected to get a copy of his notes of the exhaustion, hut speaking 

 from recollection (and I am pretty sure I am right), it was between 25 and 

 26 inches. You tiied to attain the utmost vacuum ?— I think so; it was 

 Mr. Brunei who directed those experiments. We can get 27 inches vacuum 

 on the whole line without much difficulty; hut we do not like to get it, be- 

 cause when you get to the degree of exhaustion, it increases the expenditure 

 of engine power very much ; hut I have raised the exhaustion upon the 

 whole line to 27^ inches frequently. Did you at the same time take any 

 note of the horse power .'—No ; I had no means of doing so at that time, 

 but that will n-it make a difference in these figures: it only makes a differ- 

 ence in the original power exerted in obtaining the requisite exhaustion ; it 

 takes a pro[inrtionally much longer time, in the first instance, to raise the 

 gauge to 27 inches, than to raise it to 20. 



The increase of speed is contingent in a very small degree on the pressure 

 upon the piston in the pipe — (V/t/noles.) 



"The velocity in the atmospheric system is due to the proportion between 

 the pipe and the air-pump. The speed of the stationary engine is a constant 

 speed of, we will say, three miles an hour. We will suppose, and in fact it 

 is the case, that the piston of the air-pump moves at that same velocity of 

 three miles an hour. Then the proportion between tlip area of the pipe and 

 the area of the air-pump is the exponent of the velocity ; the velocity of the 

 piston of Ihe air-pump being multiplied by the number of times that the 

 area of the air-pump is greater than the area of the pipe, will give you the 

 Velocity of the train theoretically. Ilipre is a certain amount of deduction 

 to be made from that, on account of leakage and other matters ; liut the 

 velocity of the piston regulated entirely by the velocity with which the air is 

 drawn from the tube by the air-pump; that is the reason why the velocity 

 is independent of the load ; the velocity being independent of the load, the 

 pressure upon the piston does not form an element of the velocity at all. I lay 

 down this without fear of contradiction, that the load to he carried on the 

 atmospheric railway is as the diameter of the pipe, and the pressure created 

 by the rarefaction of the air; that gives you the load to be drawn. The 

 velocity is as the proportion between the area of the air-pump and the area 



of the pump, and is totally independent of the load. There is a certaia 

 amount of power to he calculated in order to work the air-pump ; the num- 

 ber of strokes per minute must be so many, and the duration of them must 

 he for a certain time, in order to get a higher degree of pressure ; hut that 

 has nothing to do with the question in the way you have put it, as to the 

 increase of pressure upon the piston, because the increase of pressure upon 

 the piston will enable you to carry a larger load ; hut it is the increase of the 

 size of the air-pump, and the increase of the proportion between the pipe and 

 the air-pump, that regulates the velocity." 



Stationary Engines. — 1. Nature of the Stationary Engines; their 

 Operations; Cost ; probable Duration. — On the Croydon line there is a 

 double set of engines, so that one engine may perform the exhaustion before 

 another train can arrive. The same effect is proposed to be produced on the 

 South Devon line by a tank of water, which, on being emptied, leaves a rare- 

 fied atmosphere. There will be double sets of engines on the London and 

 Croydon line, which can be brought to bear upon the trains at pleasure — 

 (Samuila.) 



It is not at all necessary that these fixed engines should be high pressure — 

 {Field.) 



Those on Ihe Croydon Railway are low-pressure condensing engines, work- 

 ing the steam to 251b. upon the inch to commence with — [Samuda.) 



On the South Devon line one pair of engines will be suffitienl to draw the 

 trains 50 or 60 miles an hour. If more power he required, there must be 

 larger engin"*. Doubtful expediency of increasing the distance between the 

 engines- — {Brunei.) 



"there are advantages in having them numerous as well as disadvan- 

 tages ; by working two engines, one in front of the other, you get all the 

 advantages of double power of engine, and the probabilities of delay and in- 

 terference are less by having numerous engines, than by having larger ones 

 and fewer in nuniher ; and except the mere cost of attending to those en- 

 gines, 1 do not think that there would he any material saving." 



In the event of an increase of traffic, it would always be practicable to adJ 

 a stationary engine at each station, to increase the power — {Samuda.) 



Cost of each pair of steam-engines on the London ami Croydon line, in- 

 cluding the exhausting pumps, the expansion gear, &c., is £4240. Such en- 

 gines would continue iu good order for 20 or 30 years, as we see in the 

 waterworks — {Field.) 



2. Cost of Repairs — The average annual cost of repairs would not exceed 

 10s. per horse power, or 50/. a-year for two engines of 50 horse power. The 

 cost of repairing the engines on the Blackwall Railway has been under thii 

 proportion. The ordinary rcfiairs to keep the engines in good working order 

 might he done at night, or in the intervals. The estimate of 10s. the horse- 

 power would include the repair of the pumps — {Field.) 



Number of days the Dalkey line has been stopped during the 11 monthe 

 previously to 1st March, from fractures to the steam engines ; to what these 

 fractures are attributable — {Bergin.) 



" What was the weight of the heaviest train you ever carried ? — Seventy, 

 four tons and a half. I once tried 78 tons 17 cwt , but could not get it 

 more than ,* where it stopped, in the sharp curve of 570 feet. Upon 



the Dalkey line there were 337 days during which we were at work ; we 

 were stopped for eight and a half entire days, from fractures to the steam- 

 engine. The stoppage upon the 28th and the greater part of the 29th of 

 April arose from the pedestal of the fly-wheel shaft of the engine breaking, 

 and it was of course quite impossible to work the engine until that shaft wa» 

 repaired. And we had to stop again from the 15th to tht- 19th of -August, 

 being five days ; we were stopped then in consequence of the great crank 

 having broken, which in its fall damaged the parallel motion and the cylinder 

 cover; it took us five days to repair that acciilent, during which we could 

 not work the engine. Again, in last December we had another delay of a 

 day and a half, from a different cause ; there had been a great deal of rain, 

 and one of the banks fell down, ami obstructed the trains fur a day and a 

 half; it took that time to remove the m.iterials. We have never, from the 

 running of the fir^t train to the running of the last train upon the line, had 

 any accident to the valve, or any part of its apparatus." 



Stations. — Number of stations on the South Devon line — {Samuda.) 

 " There will be a station at Newton, which will be the extreme end of the 

 20 miles, and we shall have stations at Dawlish, Teignmouih, Saltash, and, ( 

 believe, two others, at places the names of which I do not know ; there will 

 be, I believe, five stopping stations in the 20 miles." 



By the nmoval of locomotives the complication, extent, and unsightliness 

 of railway stations would he very much reduced. It is propirsed to move the 

 carriages and add them to the train hy a small capstan, as in the goods shed 

 at Bristol— («iunc/.) 



fTo be continued.) 



■ So in tlie original. — Ed. 



The city of Paris has voted the sum of 41,600 francs (£1604) for paintings 

 on glass for the churches of St. Germain I'Auxerrois, St. Gervais, St. Eus- 

 tache and St. Laurent. 



