1845.J 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL 



373 



condensing enginp, without a beam ; the steam piston acts directly on a 

 crauk aflixed at one end of the Hy-wheel shaft. At the other end of the 

 shaft is another crank, which works the air-pump. The dimensions of 

 the engine are a S4} inch cylinder, 5 J feet stroke ; llie area of the piston 

 is therefore !I21} square inches ; the mean speed of the engine is 22^ 

 double strokes per minute; the steam is intended to enter at 4Blb. pressure 

 above the atmosphere, and it is cut oil' at a variable leiiglh from one-flfih 

 to nearly one third of the stroke, according to circumstances ; it is cut olf 

 at a fourth on a mean of all its workings." 



Weight o/ Trains. — Allusion to the statement made by Mr. Stephenson, 

 that the velocity decreased very rapidly on the atmospheric system upon 

 the increase of the weight of the train — {Cubitt.) 



'■ Have you seen Mr. Pdhrow's application of the atmospheric plan? — 

 No; I am aware of the principle of it. I did not go to see it, because I 

 did not think that I could deri\e any practical information from it. I was 

 not desirous of being seen there, lest I should be made use of to pulTolf 

 the invention. Mr, Stephenson staled yesterday, that the velocity in- 

 creased very rapidly on the atmospheric system upon the increase of the 

 weight of the train, and he gave the committee many details on the sub- 

 ject ; have you any statement to make on that jioinl? — The hea^ ier we 

 make a train, the more power it tdkes to move it. If you attempt to move 

 R large train with the same power as a light one, of course it will be re- 

 tarded. That jou can overcome? — Yes, if we take a locomotive engine 

 and a double-sized train, we must fire the engine and water it very dillcr- 

 ently to what we should do otherwise ; it is just the same in either case ; 

 a train twice as long as ordinary will take a greater force to move it. With 

 a locomotive engine you can keep increasing the ti'ain till tlie engine can- 

 not move it ; the wheels will run round, and not move over the road at all ; 

 you must then put on more power to take olf some of the load, and having 

 done so you will get on. When you require increased power from a loco- 

 motive engine, do you increase the expense of that power as much as upon 

 the atmospheric principle? — Quite, aud I think rather more, because it 

 can go up any incline ; it must be remembered too, that you have to add 

 all the power nece.ssary to propel the engine itself, besides the load which 

 it has to draw behind it. That never happens upon the atmospheric 

 system; whether it is up or down the moving force continues the same ; 

 while the moving force in the locomotive varies accordiug to the inclinalion, 

 and the power actually may be all absorbed in moving the engine up an 

 incline, and no moving force may be left to draw the train ; whereas in 

 the other case the moving force will always keep the same, aud you may 

 increas the power to any extent you please. Thet is a very ditticult thing 

 todefine; but the moving force which moves the train, and the power 

 which impels it, are two eitirely different things. With respect lo the 

 estimates that have been delivered in, what do you think would be the 

 cost per mdn of the buildings which are required for the housing of loco- 

 motive engines? — I take 1,000/. per mile for workshops and tools, and 

 8,000/. per mile per plant; that is what I estimate for the London and 

 York ; 3,000/ in all." 



IVuoden Rails. — .Supposing the price of iron to keep up, witness would 

 be induced to put down the wooden rails ; they would be perfectly appli- 

 cable to the atmospheric system — (Ci/ii//.) 



Yarmoutli and Norwich Ruilu-aij — Calculation showing the much greater 

 expense that would be incurred in working this line upon the atmospheric 

 principle — (Slepltensim.) 



" The working of this line, the Yarmouth and Norwich, is let to a con- 

 tractor for the amount of 7,000/. per annum : those are the whole of the 

 expenses. I will take olf from that 7,000/. such items of the expense as I 

 know he must incur: for instance, the government duty amounted to 800/. 

 a year; that has been actually paid. Then there is maintenance of road, 

 I assume that at 70/. per mile, that amounts to 1 ,400/. ; the salaries of the 

 clerks amount to 8U()/. ; the working of the carriages is let to Mr. M right, 

 the coach builder, who maintains them at so much per mile ; I believe he 

 has Id. per carriage per mile ; that would be 600/. ; those are all the ex- 

 penses which I assume the contractor is obliged to incur, and which he 

 does in fact incur, and that amounis to 3,600/. ; therefore ihat leaves fur 

 the costs of the locomotives 3,400/. a year, and his profit ; but I will as- 

 sume that he gets no prolit at all ; he has to do the working of this rail- 

 road, 20 miles in length, for 3,400/. a year. If you divide 3,400/. by li« 

 miles, it amounis to 170/. a mile for working the line by locomotive eu 

 gines: now this line is through country as flat as a bowling-green all the 

 way ; there is one cutting of sand near Keigham, and that is all, aud tliat 

 was made because we wauled ballast; therefore the whole 20 miles may 

 be considered as level as this table, being land recUimed from the sea 

 chiefly; the cost of working that traffic is 170/. per mile. The works 

 would not have been reduced Id if it had lieen conatrucled in the first in- 

 stance for an atmospheric line; it was laid down upon the surface of the 

 country all the «ay ; therefore assuming the cost of an atmospheric line at 

 6,000/. a mile, or at 5,000/., the simple interest of that money, at 5 per 

 cent., is 2:dl. a mile, without the expense of working the line at all : now 

 the cost of working the locomotive line is 170/. a mile ; therefore, there 

 would be the loss, if you worlted the atmospheric system, of the difl'erence 

 between 2i0/. and 170/." 



In making the calculation of the expense of adopting the atmospheric 

 system, witness did not take a tube of any particular diameter. On a 

 line of this description, and with the same amount of traffic, a tube of six 

 or seven inches would be quite sufficient— (67e;)A<;ns«n.) 



EXPLOSION OF FIRE DAMP. 



Chemical Society, Nov. 3. — "A Report on the Fire-Damp of Coal 

 Mines, ami the Means of preventing Accidents from ita Explosion," was read 

 hy Professor Graham. The author had some years a^o examined the gas of 

 these mines, v\ith the same result as Davy, namely, that it contains no other 

 combustible ingredient than light carburetted hydrogen. Hut the analysis 

 of the gas of the coal mines of Germany, sulisequently published, showing 

 the presence of other gases, particularly of olefiant gas, rendered a new ex- 

 amination of ibe gas of the English mines desirable. The gases were, (1) 

 from a seam named the Five-Quarter seam, in the Gateshead Colliery, where 

 the gas is collected as it issues, and used for lighting the mine ; (2) the gas 

 of Hepburn Colliery, which issues from a hore let down into the liensham 

 seam — a seam of coal which is highly charged with gas, and has been tne 

 cause of many accidents ; and (3) gas from Killingworth Colliery, in the 

 neigbbonrhood of Jarrow, where the last great explosion occurred. This 

 last gas issues from a fissure in a stratum of sandstone, and has been kept 

 uninterruptedly burning, as the means nf lighting the horse-road in the mine, 

 for upwards of ten years, witlinut any sensible diminution in its quantity. 

 The gases were collected personally by Mr. J. Hutchinson, with every requisite 

 precaution to insure their purity, and prevent admixture of atmoFphenc air. 

 The usual eudiometrieal process of firing the gases with oxygen was suffi- 

 cient lo prove that they all consisted of light carburetted hydrogen, with the 

 exception of a few jier cent. It was observed that phosphorus rcm:iins 

 strongly luminous in these gases, mixed with a light air, while the addiiioii 

 of one four.huiidredth part of olefiant gas, or even a smaller proportion of 

 the volatile bydro-carbon vapours, destroyed this property. Olefiant gas it- 

 self, and all the allied hydro-carbons, were thi:s excluded. Another property 

 of pure light carburetted hydrogen, observed by Mr. Grah,im, enabled him 

 to exclude other combustible gases, namely, that the former gas is capable 

 of entirely resisting the oxidating action of platinum black, and yet permits 

 other gases to be oxidated which are mixed with it even in the smallest pro- 

 portion, such as carbonic oxide and hydrogen, the first slowly and the last 

 very rapidly ; air, or oxygen gas, being, of course, also present in the mixture. 

 Now platinum black had not the smallest action on a mixture of the gas 

 from the mines with air. The gas was also inodorous, and clearly contained 

 no appreciable quantity of any other combustible gas than light carburetted 

 hydrogrii. The only adilitional matters present were nitrogen and oxygen, 

 or air; the specimen collected in the most favourable circumstances for the 

 exclusion of atmospheric air, namely, that from the Bensham scam, still con- 

 taining 0'6 per cent, of oxygen. The gases also contained no carbonic acid. 

 Attention was directed to the result that nothing oxidable at the temperature 

 of the air was found in a volatile state associated with the perfect co:il of the 

 Newcastle beds. The remarkable absence of oxidability in light carburetted 

 hydrogen appears to have preserved that alone of all the combustible gases 

 oiiginally evolved in the formation of coal, and which are still found accom- 

 panying the imperfect lignite coal of Germany, ot which the gas has been 

 examined. This fact is of geological interest, as it proves that almost inde- 

 finitely protracted oxidating action of the air must be taken into account in 

 the formation of coal ; air finding a gradual access through the thickest beds 

 of super-imposed strata, vvhctlier these strata be in a dry sta-te or humid. In 

 regard to measures for preventing the explosion of the gas in coal mines, and 

 of mitigating the effects of such accidents, Mr. Graham confined himself 

 to two suggestions. The first has reference to the Iriigth of time which the 

 fire-damp, from its lightness, continues near the roof, without mixing uni- 

 formly with the air circulating through the workings. He found that a glass 

 jar, of six inches in length and one inch in diameter, filled with fire-damp, 

 and left open with its mouth downwards, continued to retain an explosive 

 mixture for twenty minutes. Now it is very desirable that the fire-damp 

 should be mixed as soon as possible with the whole circulating stream of air, 

 as beyond a certain degree of dilution it ceases to be explosive. Mr. Buddie 

 has stated, " tliat immediately to the leeward of a blower, though for a con- 

 siderable way the current may be highly explosive, it often happens that after 

 it has travelled a greater distance in the air-course, it becoines perfectly 

 blended and mixed with the air, so that we can go into it with candles; 

 hence, before we liati llie use of the Davy lamp, we intentionally make ' long 

 runs,' for the purpose of mixing the air." It was recommended that means 

 be taken to promote an early intermixture of the tire damp and air; the 

 smallest force is snlficient for this purpose ; as a downward velocity of a few 

 inches in the second will bring the light gas from the roof to the floor. The 

 circulating stream might be agitated most easily by a light portable wheel, 

 with vanes, turned by a boy, and so placed as to impel the air in the direc- 

 tion of the ventilatioii, and not to impede the ilralt. 1 be gas at the roof 

 undoubtedly often acts as an explosive train, convcjing the combustion to a 

 great distance thnmgh the mine, while its continuity would be broken by 

 such mixing, and an explosion, when it occurred, be confined within narrower 

 limits. Secondly, no effective means exist for succouring the miners after 

 the occurrence of an explosion, although a large proportion of the deaths is 

 not occasioned by (ire, or injuries from tlie force of the explosion, but from 

 suffocation by the after-damp, or carbonic acid gas, which afterwards diflTUses 

 itself through all paits of the mine. It was sugL'csfed that a cast-iron pipe, 

 from eight to twelve inches in diameter, be permanently fixed in every shaft, 

 with blowing apparatus above, by which air could he thrown down, and 

 the shaft itself immediately ventilated after the occurrence of an explosion. 



