網頁圖片
PDF
ePub 版

importance, Railroads designed to serve as commercial thoroughfares, should in every part of the country be made on one uniform scale, that the vehicles which ply on one may be capable of plying on all. Unless this is attended to, the waggons and steam coaches adapted to one Railroad will be of as little use when brought to another, as a cart is when its load is to be carried on a Canal. Counties and districts would in truth be isolated by this want of system, and each, though provided with the most perfect railroads, would be impervious to the travelling machines of the county or district adjoining.

Nothing but experience can tell us correctly the form and proportions of a railroad best calculated for a great system of internal communication. But as we must start on some plan, in order that this provisional plan may be as perfect as possible, it is extremely desirable that we should anticipate, as far as we can, the future results of extensive practice, by experiments skilfully made on a large scale. To render these experiments satisfactory, they should not be confided to mere practical men. A person who is not thoroughly instructed in the powers and properties of matter, and the principles of mechanics, cannot devise experiments so as to meet all the difficulties of the subject; and in the results to which they lead, truths will escape his eye, which would be obvious to the man of science.' Without pretending to indicate what course is most advisable, I may observe, that there are two points which it is of much importance to determine-- what is the utmost speed practicable for the conveyance of passengers, and what is the most advantageous speed for the transportation of goods. Let us suppose, for instance, that the most eligible rate of motion is found to be 8 miles an hour for the one, and 16 for the other. One consequence would probably follow from this, that as carriages travelling rapidly could not easily pass one another on the same rails, every great railway would have two sets of paths—one for quick, and the other for slow vehicles; and it might perhaps be found expedient also to have these paths of different breadths, strengths, and dimensions. I say two sets, (that is four paths) because on all much frequented roads, one path would be required

i I understand that the Subscribers to the Edinburgh and Glasgow Railway have it in contemplation to engage Professor Leslie (with the assistance probably of Mr. Jardine and Mr. Buchanan) to make experiments for them. The iask could not be confided to betier hands. It were to be wished that some of the other great companies would unite with the Edinburgh and Glasgow Company as to this object, that the experiments may be made on as large a scale as possible. Unless something of this kind is done, it is easy to see, that many of the roads first formed will be torn up again in a few years, on account of defects in the plan.

for going and another for returning, for each class of vehicles. Perhaps for the same reason it might be found necessary to compel all vehicles to adopt one or other of these fixed rates of travelling, The weight and speed of the vehicle will determine the strength of the rails, and the uses to which it is put, will probably determine the breadth of the path. If, for example, it is intended that the steam-coach shall have the accommodations of the passage boat, the breadth of the vehicle between the wheels would require to be 6 or 8 feet, and that of the road the same. Again, it might be necessary for the rapid vehicles, that the rails should project 3 or 4 inches above the ground and the chains and sleepers, that the engine and coach might be secured against springing off the road, either by a deep flaunch on the wheel, or by a guiding rod projecting downwards, and fitted with a small roller to press against the side of the rail, the moment the wheels began to deviate. With whatever views companies start, it should be their object to obtain an ample breadth of ground: for the most obvious plan of improving railways will be, by laying down new paths on better principles by the side of the old.

It is probable that great improvements will yet be made on the waggons and locomotive engines—by employing large wheels and small axles, by using friction wheels, by making nicer work, &c.

As there are the strongest grounds to believe that Railroads will become, in a short time, the general medium of commercial intercourse, companies which have undertaken to execute such roads in particular districts, should keep their eye on this circumstance. In all great changes much is gained by proceeding on system. The geographical situation of Scotland marks out, in a general way, the direction of the main trunks, and Railways which can readily form portions of these, will have advantages over those which depend entirely on local traffic. A good Tract on this subject, by an able engineer, well acquainted with the levels, and the physical and commercial circumstances of the country, would be useful. One of the great roads from England must obviously enter by the east .coast, and the other by Carlisle. We may suppose the former continued through the middle of East Lothian to Edinburgh ; thence through Linlithgowshire to Stirling, after sending off a branchto Glasgow ; from Stirling along the valley of the Allan and the Earn to Perth; and thence by the coast to Dundee, Montrose, and Aberdeen. From Perth, however, a branch scarcely less important than the main trunk might be carried through the fertile valley of Strathmore, in the line marked out by Mr. Stevenson. The course of the Tweed will afford a separate line into Mid-Lothian, and perhaps into Lanarkshire. The most

advantageous line for the western main trunk would probably be from Carlisle to Dumfries; thence along the valley of the Nith into Ayrshire (the summit level being only about 500 feet above the sea, with an ascent remarkably regular); and by Ayr, Irvine, and Paisley, to Glasgow. A branch line would, of course, run along the coast by Wigton and Stranraer. It is not improbable, that by rails of a cheaper kind perhaps of wood, like those first used at Newcastle the benefits of this improvement may even be extended to the Highlands, which are penetrated to a great depth at various points by vallies, often deviating very little from a horizontal level. These remarks, however, are thrown out merely as hints, which may lead others who have greater advantages, to discuss the subject at large.

I have now before me the observations made by an eminent engineer, at the second trial of the locomotive engines on the 22d January at Killingsworth. The engine had two 9 inch cylinders, and a two feet stroke made on an average 51 double strokes per minute, and weighed 9 tons. The pressure was not known, but the engine was probably of 8 horse power. It dragged 12 waggons weighing 15 tons when empty, and 484 tons when filled (with 331 tons of coals), five times back and forward over an edge Railroad 1663 yards long, and rising 1-30th of an inch per yard. The greatest speed up was 6.85 miles per hour, the greatest speed down 7.4 miles; the mean 7.125; the mean of the whole journies, over 16,632 yards, (9} miles) was 6.65 miles. The common speed of the locomotive engine at Killingsworth is about 4 miles an hour; but its ordinary wheels of three feet diameter were in this case replaced by others of four feet. With regard to the nature of the road, Mr. Wood states that a great part of it“ was of cast iron rails on the old plan, the joinings of which present great resistance to the carriage wheels: the weakness of the rails, which in some parts weighed 28 pounds a yard only, also prevented the engine from being driven at the greatest speed; for where a part of the road was formed of malleable iron, the engine travelled at eight miles an hour up the plain, and at ten miles an hour down. And it was the opinion of all present, that if the Railroad had been of more modern construction, the performance would have been much greater.” He adds, “ bý using different sized wheels upon the same engine, I have found, by careful experiments, that up to a speed of seven or eight miles an hour, the performance of the engine is increased in the ratio of the diameter of the wheels used, or that the same qnantity of fuel which propels an engine over 36 miles with three feet wheels, will propel it over 48 miles with four feet wheels.” He attributes thi to the din minution of the friction, and correctly to some extent; but part of

the effect, I think, may be traced to the principle I have explained, by which, abstracting the resistance of the air, a high velocity may be commanded almost as easily as a low one. The large wheels merely served the purpose of giving effect to the power of the engine at a higher velocity without loss. In the experiment above described, when the engine with four feet wheels travelled 10 miles an hour, the piston rod must have made 70 double strokes per minute ; and in this case it is probable that fully one-third of its power was wasted in producing this very rapid motion.

The coal consumed in propelling the machine during the time it travelled 91 miles was 360 pounds. Hence, taking the speed of the engine on the more perfect part of the rails as a basis, we may assume as an element in our calculations, that 1 pound of coal suffices to drag one ton of goods (1} tons including the waggon) over one mile. The engine performs this besides moving its own weight. Taking the price of coal at 103. per ton, the expense of fuel will therefore be about 1-20th of a penny per mile for each ton, or one penny per mile for twenty tons. ."

The engine is attended by a man and boy. Supposing their united wages to be 5s., and that during the ten hours they are employed the engine drags 33 tons of goods over 60 miles; and farther, that 5s. more are paid for labor in loading tenders with water and coals, to replace one another, then we find the expense to be

sh., or 1-16th of a penny per mile for each ton. bined expense of coal and wages makes one-ninth of a penny per ton. This may be considered as the cost of traction. of loading and unloading is as much for a short journey as a long one. If estimated at 8d. per ton on a journey of 64 miles, it would be one-eighth of a penny per ton, which, added to the expense of traction, would make about one-farthing per mile, per ton. The interest of the capital sunk in the engine and waggons may be disregarded. Supposing the toll dues to be about 1d. per mile, there is no doubt that goods may be conveyed on railroads at 1}d. or 2d. per ton. I am disposed to think, therefore, that I was misled, when I stated, on the authority of an English paper, that the expense of steampower would be greater than that of horse power at low velocities. It is extremely probable that carriage by the locomotive engine will be cheaper than by horses in all cases; and I now find that this

' Mr. Wood finds that when wheels four feet in diameter are used, 513 pounds of coal drag 48} tons one mile, and this upon a railroad of variable quality. The rate of motion was about 5 miles an hour. The water consumed is about one gallon for 3 pounds of coal. Practical Treatise, p. 249-264.

? A small waggonbearing water and coals follows close behind the engine, and is called the Tender, i. e. the “ Attender."

10 33 X 60

The com

The expense

is the opinion of an eminent engineer of this city, who has examined the working of the locomotive system in all its details, on the spot. Moreover, when we recollect that these calculations are founded on experiments made with an imperfect railroad, and with vehicles less perfect than they may yet be rendered, I think we may confidently anticipate that future improvements will enable us to accomplish a great deal more with the same expenditure of fuel and labor.

This low estimate of the expense of Railway carriage, is confirmed by the testimony of Mr. Chapman, an engineer, who has had great experience in these matters. He estimates the prime cost of carriage to a company which should make a canal or railroad, and supply the vehicles themselves, as follows :-“On a canal with vessels in full employment, according as they may be more or less interrupted by locks or other circumstances, ad. to 11d. per ton per mile. By horses on level railways, including replacement of the horses, d. By locomotive machines (passing through coal districts) including interest, renewal and repairs, and in distances of ij miles or more, about 2-5ths of a penny. By stationary engines in coal districts) from 1-3d to 2-5ths of a penny. Self-acting inclined planes about 1d. The general inference he draws is, “ that, inclusive of interest of capital and repairs of machinery, the conveyance by mechanical means will only amount to from 1-3d to 2-5ths of a penny per ton per mile, under a rapid conveyance of seven miles or upwards per hour ; and that conveyance by horses whose rate of motion will fall short of three miles, will cost about id. per ton per mile.”—(Report in Newcastle Courant of 20th Nov.)

Coal is so useful a species of fuel, that it will command a sale in this country, wherever it can be afforded at a price probably not exceeding 24s. per ton. Supposing the cost at the pit mouth to be 4s., and that by reducing the tolls a little it could be conveyed and delivered at the expense of 1}d. the ton per mile, coal would in this case bear to be carried 160 miles. Hence the coal of Fife and Mid-Lothian, transported on railways, might find a market in Aberdeen and Inverness.

Grain, on account of the care required to protect it from moisture, might be charged 2d. per ton. Hence, taking the weight of 5 quarters to be equal to a ton, the wheat of Forfarshire might be conveyed to Edinburgh or Glasgow (70 miles) at 2s. 4d. per quarter, the precise sum which it costs at present to cart grain from Dalkeith to Edinburgh (six miles). Potatoes, also, which are sometimes selling at 5s. in the country, and 12s. or 15s. in the capital, would have their price enhanced only about 2s. by conveyance over a distance of 50 miles. But the cheapness of the carriage is but a part of the advantage; for we must recollect, that the commodities carVOL. XXVI.

Pam.
NO. LI.

F2

« 上一頁繼續 »