Part 6

But supposing ten times this load were to be raised, the degree of exhaustion must be ten times as great, or about the fourth of a vacuum. And, as the greater the exhaustion, the less the expansive power, and, consequently the less the inertia and friction of the air inside the exhausted part of the tunnel, this “rope of air” as it has, derisively, been called, possesses the important advantage of decreasing as relates to the density, inertia, and friction, which _itself_ opposes, in proportion to the increase of the load drawn by it: while, as the valves I should place at every quarter, or half, or whole mile, to be opened by the carriages as they pass them, and admit air immediately behind said carriages, would prevent there being the inertia and friction of more than a few hundred yards of air of the _natural_ density behind the carriages to be overcome, the impediment which presents an insuperable obstacle in the opinion of the numbers who have condemned the proposition (because they deemed operating by exhaustion the same as operating per plenum) diminishes, in point of fact, to a far less important hindrance, than that which is occasioned by the old system of drawing loads by means of stationary engines and ropes; since, in the present instance, the inertia and friction would not be the one-hundred-and-sixtieth part of what it would be, to move an equal quantity by the stationary engine, and rope system.

And notwithstanding that the superiority which the tunnel possesses over the locomotive system is not so great at this, yet is it important.

In the instructions given to Mr. Walker by the Directors of the Liverpool and Manchester Railway (and which called from him the Report criticised by Messrs. R. Stephenson and Locke), it is stated that “the quantity of traffic for which it will be expedient to provide the power of conveyance” is about 4000 tons, from each to the other of those places, daily.

In his publication on the Liverpool and Manchester Railway, Dr. Lardner says, “In the experiments which I have detailed, it appears that a steam engine is capable of drawing 90 tons at the rate of about 20 miles an hour; and that it could transport that weight twice between Liverpool and Manchester in about three hours.” {38a} The weight of this engine alone being 8.1 tons, the whole weight of itself, and its tender, with the necessary supplies of fuel and water, will not be less than twelve tons. Therefore, the friction of the engines (and their tenders) requisite to carry these 4000 tons at the rate of 20 miles an hour, would be 4267 lbs.

The friction of one mile of air in a tunnel eight feet in diameter, when moved at the rate of 20 miles an hour by _exhaustion_ being 288lbs., the friction of it in a tunnel extending from Liverpool to Manchester, will be 8640lbs.: which, though double the friction of these locomotive engines, might be far cheaper for the following reason; and independent of the circumstance, that I could lay down a tunnel capable of carrying all these 4000 tons at one and the same time, from Liverpool to Manchester, for one-fourth of what that railway has cost; {38b} and also independent of the circumstance that the enormous expense now incurred for the repairs of the locomotives (as stated on page 11) would also be saved.

It is well known that the smaller a steam-engine is, the larger is the proportionate quantity of fuel it requires, and the greater the proportionate expense of working it; while it is equally well known that, owing to the imperative importance of lightness and efficiency over economy in locomotive engines, this disadvantage increases in a most rapid ratio with respect to them. In consequence of this, a quantity of fuel, which, in large stationary engines, such as I should use for exhausting air from the tunnel, would do a given quantity of work, would, in the best of the locomotives on the Liverpool and Manchester Railway, do only one-sixteenth as much work.

Therefore it results, that, notwithstanding the friction of the air in a tunnel 30 miles long would, at the rate of 20 miles an hour, be twice as much as the friction of the locomotive engines, yet, owing to the fuel consumed by the latter, to move themselves and their tenders, being sixteen times as great as large stationary engines, such as I should use, would require to do the same work, the tunnel would, supposing the whole quantity of goods were to be carried at once, be eight times the cheapest mean of conveyance, in point of current expenses only, and without reference to its first cost being only one-fourth that of the railway; and also without reference to the whole of the enormous expense now occasioned by the repairs of the locomotive engines being saved.

But this is not the only proportion in which a tunnel might be cheaper. The 13th paragraph of the Russian Engineer Officer’s Report, states, that he is “convinced that exhaustion to a degree which should give a pressure of fifteen inches of mercury may be effected in the tunnel.” Now, notwithstanding that much more than this may be done in an iron tunnel, yet will I calculate on this only. Fifteen inches of mercury being 7.3 lbs. that pressure on the area of the tunnel, would move above twice the 4000 tons which the Directors of the Liverpool and Manchester Railway estimated would be carried from one to the other of those places every day; which, supposing that weight to be conveyed at one time, would reduce the expense (per ton of goods carried) of overcoming the friction of air moving in a tunnel from Liverpool to Manchester, at the rate of 20 miles an hour, to one-sixteenth of what the power required to overcome the friction of the locomotive engines required to draw the same weight would cost.

And though, owing to its being a received opinion that the power required to overcome the friction of fluids increases according to the square of the velocity, we are to suppose that at 40 miles an hour, the fuel required to overcome the friction of the air would be one-fourth that of the locomotive engines, while at 80 miles an hour it would be equal to that of the engines, still would a quadruple velocity be attained, by the expenditure of only an equal quantity of fuel.

The amount of the power required to overcome the friction of the locomotive engines (and their tenders) necessary to carry 4000 tons weight from Liverpool to Manchester daily, at the rate of 20 miles an hour, is, when expressed in “horse’ power” equal to the power of 225 horses working for an hour and a half. In other words, these locomotives must exert power to this amount, beyond what is required to draw the 4000 tons weight.

The power required to overcome the friction of air, which was moving (by exhaustion) at the rate of 20 miles an hour, in a tunnel of eight feet diameter, extending from Liverpool to Manchester, would be equal to that of 456 horses: which, though double the preceding, would yet be eight times cheaper, owing to large stationary engines, such as I should use, requiring only one-sixteenth part of the fuel required by locomotives to do equal work.

At 40 miles an hour (supposing locomotives could go so fast) the number of horses’ power required to overcome the friction of the air in the tunnel would (according to the received opinion of that friction increasing to the square of the velocity) be 3650: which, though sixteen times greater than that of the locomotive engines and their tenders, yet, in consequence of this power being exerted only for three-quarters of an hour, instead of an hour and a half, and of fuel doing sixteen times as much work in large stationary engines as in locomotives, would be only half so expensive as the locomotives and their tenders would prove.

At 80 miles an hour (which is twice as fast as locomotives can go) the power required to overcome the friction of the air in the tunnel, would (on the calculation that it increases according to the square of the velocity) be equal to that of 29,196 horses; which is nearly 130 times as much as the locomotive engines would require: though, owing to this power operating only 22½ minutes, instead of an hour and a half, and to fuel in large stationary engines doing sixteen times as much work as in locomotives, the expense would be only twice as great as in the locomotives, exclusive of the whole of the most enormous expense now incurred, by the repairs of the locomotives being saved (which would, alone, more than make up the difference) and also exclusive of the tunnel costing only one quarter of what the railway has cost, and of the rate of conveyance being four times as fast.

But it is not with respect to a tunnel only, that the resistance of the air opposes an impediment: this resistance being found so serious an obstacle to the progress of the locomotive engines and their loads, that in all trials of, or experiments with them, the state and direction of the wind is noted and allowed for. In the “Account of the Liverpool and Manchester Railway,” published by the Treasurer of that Company (H. Booth, Esq.), he says: “Moreover, at great velocities, the resistance of the air must not be left out of the calculation. At ten miles per hour, it has been found by experiment, that the resistance of the atmosphere is about half a pound weight on a square foot of flat surface; at fifteen miles, the resistance is 1lb. per square foot; and at twenty miles, about 2lbs. per square foot: the increased resistance being, nearly, as the squares of the velocities.” {40}

The surface opposed to the air by a steam-coach, the engines of which its proprietor told me were equal to ten horses power, I found to be 30 square feet. That, opposed by another, the engines of which were said to be equal to twenty horses power, I found to be above 50 square feet: while, when carrying four outsides on the front of the roof, this coach exposed nearly 70 square feet to the action of the air. The surface opposed to the air by the large locomotive engines now used on the Liverpool and Manchester Railway, I understand (when chimney, axle-tree, wheels, and every thing that cuts the air, is taken into account) to be about 40 feet square. Supposing it to be so, at 20 miles an hour, the air will oppose resistance equal to 80lbs. to the progress of the engine; which resistance having to be overcome at the rate of 1760 feet per minute, is equal to 4¼ horses power. At 40 miles an hour, this resistance would be 320lbs.; which resistance having to be overcome at the rate of 3526 feet per minute, would be equal to 34 horses power. At 80 miles an hour, the resistance of the air would be 1280lbs.; which resistance, having to be overcome at the rate of 7,040 feet per minute, would be equal to 270 horses power; while at 100, and 120 miles an hour, the power required would be, respectively, that of 528 and 912 horses.

Now, as the force required at 80 miles an hour, is a _few_ times more than the whole power of those engines, and as Dr. Hutton found that giving the moving body the form of a cone, the height of which equalled the diameter of its base, diminished the resistance of the air only half, it may serve to shew that the statements of those who have given currency to the opinion that we may be conveyed at _any_ velocity on railways, are promulgated by persons who pronounce upon questions without examining them: since, in addition to this resistance of the _air_ to the locomotive engines themselves, would be its resistance to the tenders, and coaches or waggons they drew; and that, too, independent of, and additional to, the resistance opposed by the _railway_ friction of the engines, tenders, and loads, behind them.

That something of this kind prevents _very_ high velocities from being attained on railways, is evident. At the locomotive engine competition on the Liverpool and Manchester Railway four years ago, velocities of from 35 to 40 miles an hour, were attained by engines which were not one-tenth the power of some of those now used; while, at the opening of that railway, three years ago, the engine by which the surgeon was brought to Mr. Huskisson, after his deplorable accident, went 15 miles in 25 minutes, which is at the rate of 36 miles an hour. Yet do not the so much more powerful locomotives now used on that road, go faster than this: a circumstance which may prove that the limit to the velocity of railway conveyance, will arise from a source not calculated on.

“But,” it may be observed, “this objection to the possibility of very high velocities on railways, is counterbalanced by the dilemma in which you place yourself, by supposing it to be possible that any such power as that of 29,196 horses, can, at one time, be made to operate on a tunnel; since, as relates to practical application, it would prove ‘an impossible quantity.’”

The inference I deny; and, when necessary, will disprove. {41} But the term I accept; and will avail myself of, to shew that it is equally “an impossible quantity” that even if a tunnel were ten times as long as one between Manchester and Liverpool, the friction of air which is caused to move in it, in consequence of exhaustion taking place at the opposite end, can ever oppose an impediment such as is here adverted to.

According to the opinion that the friction of the air would increase as the square of the velocity, the friction of the column of air, which, when moved by exhaustion at the rate of 20 miles an hour, in a tunnel eight feet diameter and a mile long, was 288lbs., would, when moved at the rate of 80 miles an hour, be 4608lbs.; which, on the whole area of the tunnel, would be equal to 1.3 inches of mercury. Therefore, supposing that at every mile of a tunnel extending from Liverpool to Manchester, barometer tubes were to be inserted, the bottoms (or basin ends) of which should be open to the atmosphere, and the tops open to the inside of the tunnel, the mercury in each successive tube would (reckoning _towards_ the end at which the exhaustion took place) rise 1.3 inches higher than that in the preceding.

Now as 1.3×23 gives 30, while 1.3×30 gives 39, it appears that at 23 miles from that end of the tunnel at which the atmosphere was admitted, and seven from that where the exhaustion took place, there would be such a vacuum as would raise mercury the _whole_ height of the barometric column; while, at the end of the 30 miles there would be—or rather _ought_ to be, according to this calculation—39 inches of mercury; or a vacuum and a third; which, in addition to its being “an impossible quantity,” places those who contend that the resistance of the friction of air which is caused to move through a tunnel by the pressure of the atmosphere in consequence of exhaustion taking place at the opposite end, increases according to the square of the velocity, in the dilemma of assuming that there is a certain place in a tunnel 30 miles long, where, notwithstanding that a man, a horse, or even an elephant, might walk as freely and unobstructedly along, as a mouse could through a rat-hole, that subtle, permeating, and all-pervading element which we breathe, would, like the stream of the Jordan when under the influence of the miracle by which the Israelites passed over that river, stop, stick fast, and be unable to move farther; a position, which necessarily throws us for an escape from this dilemma, on the conclusion that, though it is certain that the friction of air against the inside of the tunnel will be an impediment, and though it is probable that this impediment will be of some importance, yet must it be equally certain that it will not be the serious impediment which it is _supposed_ it will prove: and it may therefore, safely be assumed, that the objection which presents an insuperable obstacle in the minds of the many who have condemned the method of operation by exhaustion which I propose (because they deemed it analogous to operating per plenum) becomes removed, and is found to be what all the other “insuperable objections” which have been arrayed against the proposition are found to be when grappled with; i.e. baseless and unreal: it being necessary only to put a valve at every half, or quarter of a mile, which should be opened by the carriages as they passed, to render the length of the column of air of the natural density, which _must_ be behind the carriages to drive them along, only a few hundred yards, and its friction consequently unimportant; said valves being (as can easily be done) so arranged, as to close themselves again the moment the carriage had arrived at, opened, and passed by, the next succeeding one.

But though I freely admit that the friction of the air against the inside of the tunnel may waste power to a degree which shall prove not unimportant, yet may it be doubted whether it will be more important than the waste of power occasioned by the present method of railway transmission by locomotive engines.

In the documents laid before the Lords’ Committees on the London and Birmingham Railway, by the Treasurer of the Liverpool and Manchester Railway, on the 28th June, 1832, it is stated that the “number of trips of thirty miles” performed (or travelled) by the locomotive engines between Liverpool and Manchester, in the half year ending the 31st December, 1831, was “5392”: which, as the same document shews that the _whole_ amount of profitable weight conveyed over those 30 miles during that half year was less than 91,000 tons, gives an average of only 17 tons as the profitable weight carried each “trip.” The weight of the engines by which these loads were drawn it may be difficult to fix upon: though, as the locomotives now used on that railway, are, some of them, above six tons, others above eight, and others above ten tons in weight, it may, perhaps, be fair to take eight tons as the average weight. The weight of the tenders with fuel and water, appears to be rather a delicate subject. The weight of the tender of the Rocket, with its load of fuel and water, at the grand locomotive engine competition in October, 1829, was three-fourths that of the engine itself. There have since been many accounts of immense loads drawn on the railway, of which those by Dr. Lardner, in his “Lectures on the Steam Engine,” are considered as “by authority.” But though we find the weights of the engines, as well as of the loads, and various other particulars (even to the state of the wind) given, yet does it happen that the weights of the tenders, with their supplies of fuel and water, are “unascertained” and omitted, throughout. Under these circumstances, I can do no other than act on the best information I have obtained, and suppose the weight of the engines and tenders with their cargoes of fuel and water to be twelve tons for each “trip.”

Assuming it to be so, the weight of the moving power will be above two-thirds of the profitable weight conveyed; while, supposing the same proportion to obtain as to the 4000 tons just mentioned, the amount of the effect of the friction of the power by which they were conveyed at the rate of 20 miles an hour, would be twice and a half as much as the friction of the air would be in a tunnel when twice the tonnage was conveyed from Liverpool to Manchester in it, at the same rate; which, for equal quantities, is five times the friction while, as relates to the fuel consumed, it would be _very_ many more times than this, dearer.

There is one class, who, above all others, might derive benefit from properly considering what I thus submit, relative to the friction of the air.

When what was termed “the railway mania” was at its height, it was calculated that no body of men would be so much benefited by it as the iron trade; in proof of which the following statement was circulated:—

“We are authorised to state, that the rail-roads already projected, will require considerably more than two millions of tons of iron. Now, as iron has recently advanced from 7_l._ to 14_l._ per ton, it appears that the iron masters (by the way, the originators of, or principals in, many of these schemes) will receive from the subscribers twenty-eight millions sterling.”

But, instead of the iron trade having been benefited by the principal portion of what is expended on railways being for their article, scarcely more than one-twentieth-part has been expended for iron; the remainder having gone for labour in “cutting and embanking,” &c. &c.

In the account in Mr. Treasurer Booth’s book, of the expenses of the Liverpool and Manchester Railway, the line which, in the statement, runs “Iron rail account,” gives only 66,830_l._ as paid to the iron masters: the other hundreds, which make up the aggregate of 67,912_l._ there mentioned, being for “oak plugs, freights, und cartages;” which is little more than one-twentieth part of the whole that has been expended on this railway.

The rails of the London and Birmingham Railway are to be half as heavy again as those of the Liverpool and Manchester Railway. Yet does the expense of the “rails, chairs, keys, and pins,” in the estimate of that railway laid before Parliament, amount to only 212,940: one twelfth, that is, of the two millions and a half, which form the aggregate of the estimate there given in.

One of the inducements which railway advocates have held out to the landed proprietors of the Houses of Parliament, in order to lead them to support railway bills, has been the degree to which poor rates, &c. would be diminished, in consequence of the labourers there would be employed in digging out the earth for the cuttings and embankments, in the different parishes through which the lines of railway would run; and in the papers of the end of June and the beginning of July (1832) is a _very_ long advertisement of the London and Birmingham Railway Company, one part of which states that “The _landed interest_ will be benefitted by the expenditure of _upwards_ of two millions of the capital of the Company in labour.”

According to their own shewing, therefore, the expenditure for the benefit of the landed interest will be “_upwards_ of two millions,” while the cost of the iron rails, &c. will be only upwards of two hundred thousand pounds. And as both this, and other advertisements, and the evidence before Parliament, announce the extension of the railway from Birmingham to Liverpool, when this first half of it from London to Birmingham is done—which extension will be about the same length as this first half—the statements of the railway advocates themselves, give the iron masters to see, that the result of the time, trouble, and expense, which they (the iron masters) have devoted to bring forward railways, is, to put more than a shilling into the pockets of the agricultural interest (by the degree to which they will save parish rates, &c. &c.) for every farthing they put into the pockets of the iron masters themselves; all that is saved to country parishes, being actual gain to the agricultural interest; while the 12th or 16th paid to the iron trade is for value in iron; out of which the usual trade profit is all that the iron masters will gain. In other words, about four millions sterling will be paid _for_ the parishes between London and Liverpool, in the shape of wages for labourers, while only about four hundred thousand pounds will be paid _to_ the iron masters for the iron rails, &c.; out of which the iron masters will have to pay the wages of their men who smelt &c. the iron, and the royalties (or rent) for the ore, coal, &c. &c. used in making it.

The difference there is in the specific gravities of ore, coal, and limestone, in different places, will render any estimate _not_ correct for every place; though, generally speaking, I believe it may be received that the quantity of iron stone, coal, and lime stone, which it is necessary to raise to produce a ton of pig iron, will be about 6½ cubic yards.