EXTRACT

FROM

THE PAMPHLET ON RAIL-WAYS,

REFERRED TO IN PAGE 54.

It will eventually be seen, that there are, perhaps, none who more, or even so highly, uphold the principle on which transmission by rail-ways depends, as he who thus controverts the practicability, belief in which is the chief inducement to their being subscribed to. But the highest sense of the value of this principle, when properly applied, ought not to cause blindness relative to the impediments there are to any such increase of the rate at which we travel, as shall come up to the expectations the public have been caused to entertain relative to common rail-ways.

Overlooking the circumstances which constitute the real impediments to any such increase of velocity, it is assumed, that as we have the power of causing steam-engines to drive the wheels of fixed machinery at any rate we please, so have we the power of causing them to drive the wheels of locomotive machines at a similar rate; and that it needs but to connect the cranks of locomotive engines to the wheels on which they travel, by proper machinery, to enable us to double, triple, quadru ple, quintuple, &c. &c., the rate at which those wheels revolve, and consequently the velocity with which the vehicle moves forward. A little investigation will, however, give us to perceive, that this opinion may prove erroneous.

The motion of any loco-motive machine which is driven by fluids, such as steam or air, acting on pistons, must depend, in the first instance, on the number of strokes those pistons make in a minute.

The strokes of all fixed steam engines are limited to a certain number per minute; and cannot, without incurring the risk of the engine's tearing itself in pieces, be increased much beyond that number. If, therefore, there is a limit to the strokes, even of an engine, which, from being fixed, will admit of the utmost possible firmness being given to all the parts, how much greater must be the necessity of a limit to the number of the strokes of those which are locomotive? The rate beyond which it is ascertained the piston of a fixed engine ought not to move, is 220 feet per minute, 2 miles an hour, that is; and if, to place the question in the most favourable light, we suppose that the pistons of loco-motive engines may, by methods yet to be discovered, be enabled to work properly when moving with twice that velocity, still will their rate fall vastly short of that at which we now travel. With reference to the first cause of motion in locomotive engines, there appears then an impediment to any velocity inuch exceeding five miles an hour.

But, it will be observed, the rate at which the vehicle moves depends, not on the velocity of the pistons, but on the size of the wheels, and the number of times the action of the pistons causes them to revolve per minute. Admitted; and thence may arise another difficulty. Theory and practice appear to prove that no locomotive engine ought to make above fifty strokes a minute. They also appear to prove, that the wheels on which loco-motive engines move, ought not to exceed 3,18 feet in diameter. Supposing both these extremes to be come up to, the motion will not equal six miles an hour. To increase it beyond that, one of three things must be done. Either the pistons must make more strokes per minute than is considered safe; or the wheels must be increased beyond the size which theory and practice combine to prove ought not to beexceeded; or intermediate gearing, to render the revolutions of the wheels more numerous than the strokes of the pistons, must be made use of.

By the first, the danger of accident to the machinery would be increased, in a proportion which would appear to put it out of the question. The impropriety of increasing the diameter of wheels, which are to carry from five to ten tons, at rates many times faster than the strongest carrier's waggons dare go with the same load, and which are not merely to equal, but also greatly exceed those at which the mails travel, would appear to reply decidedly in the negative to the second.

And though the third may, at the expence of part of the

1 Some eight-horse locomotive engines are stated to weigh eight tons, others little more than five.

power of the engine, be effected, yet will doing it but bring additional opposing circumstances into consideration.

Against travelling with any velocity horses can draw us on common road, there is no impediment, owing to the wheels touching the road only on their peripheries, and being consequently free to vibrate or quiver, and trivially deflect from the exact right line, as is inseparable from the wheels of a vehicle in rapid motion.

But it is a question, whether the attrition which must unavoidably take place between the side of the wheels and the flanches of the rails, or the flanches on the wheels and the sides of the rails (as edge or flat rail-roads are used) will not oppose an insuperable impediment to any increase of velocity, greatly beyond that at which goods are now conveyed on rail-ways1.

Another question to which it seems difficult satisfactorily to reply, is," Can locomotive engines be guided with the requisite nicety, when moving at a rate much exceeding that at which they now travel? On a common road, a vehicle can be guided under almost any velocity, owing to its being quite immaterial whether it moves in an exact right line, provided the line of the road is kept; but on a road which will not ad

1 Mr. H. R. Palmer's treatise on Rail-ways, specifies some particulars relative to this and following considerations. "The power that gives the motion is necessarily at a great distance from some of the car. riages, and if the line be irregular, the power will not be exerted in the direction of the motion of the carriages: their motion will consequently be partly directed by the re-action of the flanches on the sides of the rails, and the amount of that re-action is deducted from the effect which the power might otherwise produce; and as much power as is equal to that re-action is exerted to displace the position of the rails. But it is not enough that the general arrangement of the line be as free as possible from bends; if the parts themselves do not nicely correspond to it, a resistance is encountered which is not necessary in principle. Some arrangement is always necessary to preserve the direction of the earriage. On tram ways. the flanches on the plates serve that purpose; on flat-edged rail-ways, flanches on the wheels are necessary; and the smallest imperfection in the rails will occasion a continual rubbing of the one against the other, making a resistance greater than that of the imperfection of surfaces; and every such action tends to disturb or loosen the rails, and the foundation on which they stand.

"In tram roads, the rims of the wheels are generally so far out of proportion to the strength of the materials, that, by successive motion, they form a rut or groove in the plates, and ultimately divide them longitudinally into two parts. The object of the small width is principally to pass the obstructions lying upon the rails the more easily. When any such irregularity is once found, the wheels, from other imperfections in the works, do not follow uninterruptedly the courses of those ruts, but are frequently escaping upon the sides of them, and, returning again, act with a violence on the rails, which tends to disturb their position, and produce frequent fractures."

mit of the slightest deviation from the right line, without danger of (what even now is no unusual occurrence) the wheels gathering upon, and running over the rails, it becomes an important question whether loco-motive engines can be guided with sufficient accuracy, to prevent imminent danger of being overturned, when going above six miles an hour? With horses, it certainly would not be safe to travel on railroads at any greater rate; for were they to start, or in any way deflect from the line they ought to follow, over the vehicle must inevitably go; and it is not seen how we could be secured from it, if drawn by locomotive engines. The windings, too inseparable from rail-ways, will so greatly increase the danger of accidents of this nature, that it may well be doubted, whether a velocity exceeding six miles an hour can, consistent with safety, be attained on them.

Another question on the same subject is, "would it be proper to travel on them with a velocity exceeding six miles an hour, when it would be impossible to steer clear of any impediment, whether great or small, which accident might place in the track?" On a coach, a touch of the rein will enable us to clear any stone, over which it would be ill-judged to attempt forcing the wheel; and impediments of a more serious nature may be avoided by taking the other side of the road. But when moving in a track from which it is impossible to deviate, we cannot steer clear of any impediment which accident may interpose; and how far this will be consistent with safety, under a velocity at all considerable, need not be pointed out.

It should seem, therefore, that although intermediate gearing between the crank shaft, and the wheels on which the vehicle moves, will admit of locomotive engines being moved a greater space than their pistons pass through in an hour, yet that there are other impediments to a rate greater than six miles an hour being attained, which appear inconsistent with safety.

So far the theory of this part of the question. With reference to the practice, it is asked, "Is there any instance of a locomotive engine travelling-not twenty, nor fifteen, nor twelve-but ten, or even eight miles an hour, regularly, and as a constant rate?" It is replied, No, not one. Four and five miles an hour, it is known they do get over, and that too with enormous loads.

But there is no instance of any locomotive engine having (regularly, and as a constant rate) travelled faster than, if so fast as, six miles an hour.

It would appear then, that instead of the speed at which

we can be conveyed by locomotive engines on rail roads, coming up to the greatest we can exist under, it will not exceed, if indeed it equals, that at which coaches convey us.

No one, therefore, who embarks capital in rail-ways can sit himself down with any assurance that the expedition which may be made on them will be what it shall prove impossible to exceed; and that such capital will be secure from a depreciation, similar to what is now taking place relative to canal property.

The condition next to be considered is, whether rail-ways give us the power of rendering our progress continuous and unremitting, from the commencement to the termination of the journey?

This condition needs no discussing as relates to horses; and from its being stated, that an eight-horse locomotive engine consumes nearly 2 bushels of coals and 65 gallons of water, to convey 16 tons about 4 miles an hour, the question must be decided in the negative with reference to them.

The last condition is, transmission at the least possible expense: with reference to which it is to be observed, that the current expense of engines, in which power is obtained by the operation of fluids (such as steam or air) on pistons working in cylinders, depends so much on the friction of the parts, that large engines must necessarily be worked more cheaply than small ones. Referring to what appear the most effective of the locomotive engines in use, and which are pronounced from eight to ten horses' power, we find the working cylinder to be eight inches in diameter. The area of a circle eight inches in diameter, is, to the circumference, as two to one. The cylinders of large engines are, some of them, above 80 inches in diameter. The area of a circle 80 inches in diameter, is, to its circumference, as 20 to 1. In a cylinder of this size, there can, consequently, be only onetenth of the (proportionate) friction there is in one of the former size. Now as the friction of the piston against the cylinder, when the packing happens to be screwed too tight, is sometimes sufficient, not merely to clog, but absolutely to stop the engine, it may be conceived, that engines in which the liability to this is only as 1 to 20, must be more economical than those in which this liability is as 1 to 2; and, consequently, that large engines are more economical than small ones, without adverting to the other circumstances which combine to render them so.

And if diminution of size operates thus disadvantageously, with reference to engines which, from being fixed, admit of all possible economy being exercised in working them, how