to aid him in the matter, advising them not to proceed with it. In fig. 136 a we give a lateral of the steam-carriage model as constructed by Symington; d the cylinder; e, boiler, supplied from the condenser; ƒƒ, direction pulleys; g, condenser; h, steam-pipe; i, water-tank; a, drum fixed on the hind axle; b, tooth and ratchet-wheels; c, rack-rods, one on each side of the drum, the alternate action of which upon the teeth and ratchet-wheels produces the rotatory motion.

In a previous chapter, we described the high-pressure engine patented by Messrs. Trevethick and Vivian; in the patent they claimed its employment in "propelling wheel-carriages of every description." In 1804, Mr. Trevethick set an engine to work on a very indifferent railroad at Merthyr Tydvil Colliery, in Wales; this worked very satisfactorily, and up to 1830 or 1831, it was the form which, more or less modified, was working the railroads on which steam was employed. "The advantages," says Trevethick in his evidence before the Committee of the House of Commons on carriages for common roads, "gained by this improvement, were a detached engine, independent of all fixtures, working with five times the power of Bolton and Watt's engine, without condensing water, and the fire enclosed in the boiler surrounded with water, and a force-draught created by the steam for the purpose of working on the roads without a high chimney; and from this was copied all the boilers for navigation-engines, which without could not have been available, this being independent of brick-work, light, safe from fire, and occupying little room.' The following is a description of this engine: the boiler is cylindrical, as a a, fig. 137; b is the fire-place; e the fire-door; c the entrance of the flue, which is turned before entering the chimney. By this arrangement the economy of fuel effected was very considerable, the greater portion of the heat being given out by the furnace and flue to the water surrounding them. The lower part of the cylinder was placed within the boiler, as at d, and the upper portion was surrounded by a jacket, in the space between which and the cylinder the steam from the boiler was allowed to circulate freely; the loss of steam from condensation was by this means obviated. The steam was admitted above and below the piston by the four-way cock already described; and after working the piston, instead of passing it to the atmosphere, it was led by a pipe to the chimney. By this arrangement the draught of the furnace was greatly increased, and a convenient means established of getting rid of the waste steam. Had this plan been patented, the inventor would have probably reaped a golden harvest from this alone.

The piston-rod had a cross-head attached to it, as e, fig. 138, sliding in the parallel guides f, attached to the upper end of the cylinder, and steadied by a stay as at g; from both ends of this cross-head connectingrods d proceeded, and were connected to the crank e, fixed on the centre of the driving-wheel a; the axis of the driving-wheel passing with the carriage, and immediately beneath the cylinder. The principle of this arrangement is shown in fig. 151, p. 79, Mechanics and Mechanism. This engine, on its first trial, in which the propulsion was effected by the adhesion of the wheels on the rails, drew ten tons of bar-iron, besides the carriages, for nine miles, at the rate of five miles an hour, without stopping, and carrying its heavy load of fuel and water.

α

d

9

h

fig. 138.

a

We have now to notice the ingenious mechanism introduced to obviate an inconvenience in engine propulsion which only existed in imagination. With reference to this point, Dr. Lardner remarks: "It is a singular fact, that in the history of this invention, considerable time and great ingenuity were vainly expended in attempting to overcome a difficulty, which in the end turned out to be purely imaginary. To comprehend distinctly the manner in which a wheel-carriage is propelled by steam, suppose that a pin or handle is attached to the spoke of the wheel at some distance from its centre; and that a force is applied to this pin in such a manner, as to make the wheel revolve; if the face of the wheel and the surface of the road were absolutely smooth and free from friction, so that the face of the wheel would slide without resistance upon the road, then the effect of this force, thus applied, would be merely to cause the wheel to turn round; the carriage being stationary, the surface of the wheel would slide or slip upon the road as the wheel is made to revolve. But if, on the other hand, the pressure of the face of the wheel upon the road is such as to produce between them such a degree of adhesion as will render it impossible for the wheel to slide or slip upon the road by the force which is applied to it, the consequence will be, that the wheel will roll upon the road, and the carriage will be moved forward through a distance equal to the circumference of the wheel each time it performs a complete revolution. It is obvious that both of these effects may be partially produced; the adhesion of the wheel to the road may be insufficient to prevent stopping altogether, and yet it may be sufficient to prevent the wheel from slipping as fast as it revolves. Under such circumstances the carriage would advance, and the wheel would slip. The progressive motion of the carriage during one complete revolution of the wheel would be equal to the difference between the complete circumference of the wheel and the portion through which, in one revolution, it has slipped When the construction of travelling steam-engines first engaged the attention of engineers, and for a considerable period afterwards,

a notion was impressed upon their minds that the adhesion between the face of the wheel and the surface of the road must necessarily be of very small amount; and that, in every practical case, the wheels thus driven would either slip altogether, and produce no advance of the carriage, or that a considerable portion of the impelling power would be lost by the partial slipping or sliding of the wheels. It is singular that it should never have occurred to the many ingenious persons, who for several years were engaged in such experiments and speculations, to ascertain by experiment the actual amount of adhesion in any particular case between the wheels and the road. Had they done so, we should probably now have found locomotive engines in a more advanced state than that to which they have attained."

Space will not allow of our illustrating all the mechanisms introduced to obviate this imaginary difficulty,-indeed, this, for the purposes of our treatise, is not at all necessary; we shall merely glance at the nature of a few of the most ingenious of these. Trevethick and Vivian, in their patent, claimed the plan of making, in certain cases, the external periphery of the driving-wheels "uneven, by projecting heads of nails, or bolts, or cross grooves, or fittings to railroads when required; and that in cases of hard pull we cause a lever bolt, or claw, to project through the rim of one or both of the said wheels, so as to take a hold of the ground." But, so far from adopting these contrivances at all times and under all circumstances, as a means of overcoming the imaginary difficulty before alluded to, they on the contrary expressly stated, that "in general the ordinary structure or figure of the external surface of these (the driving) wheels will be found to answer the intended purpose."

In 1811 Mr. Blenkinsop patented "certain mechanical means, by which the conveyance of coals, minerals, and other articles is facilitated, and the expense attending the same rendered less than heretofore." In this arrangement, a rack or toothed rail was laid down along one side of the railway; into the teeth of this rack a large toothed wheel worked, this receiving a circular motion from a steam-engine; the boiler and engine working this being supported by a frame on four wheels. By this means the engine was pulled along the rails, and was enabled to ascend gradients of considerable incline. The boiler was placed on a wooden or cast-iron frame; through the interior of the boiler a large tube was passed, containing the furnace; this tube was continued through the other end,

e

and bent upwards to form the chimney. Two cylinders were placed at the top of the boiler, and the pistons were connected by cross-heads and connecting-rods, f, e, fig. 139, to the cranks, c, d, fastened in the centre of two toothed wheels represented by dotted circles. These worked into a large toothed wheel placed in the inside of the cogged wheel a; the cogs in this working into the teeth or cogs placed along one side of the railway bb. The engine was long used on the Middleton Colliery Railway, near Leeds. The following particulars were forwarded by the patentee to Sir John Sinclair-With two eight-inch cylinders, the engine weighs five

fig. 139.

tons, "consumes two-thirds of a hundredweight of coals, and fifty gallons of water per hour; draws twenty-seven wagons, weighing ninety-four tons, on a dead level, at three and a half miles per hour; or fifteen tons up an ascent of two inches in the yard; when lightly loaded' it travels ten miles an hour, does the work of sixteen horses in twelve hours, and costs 4001."

We now approach the period at which two men appeared in the arena of invention; men who, up to the period of their death, were intimately connected with railway mechanism, and who were destined, during long and active lives, to be the means of introducing improvements in this branch of engineering, so effective as to cause quite a revolution in the art of travelling; these men are the well-known George Stephenson and Timothy Hackworth. To the former we are indebted for the system of railways as now established; to the latter nearly all the improvements in the locomotive which formed it the powerful and effective machine we now see it, owed their origin. And in thus paying to Hackworth part of the tribute of praise which has hitherto been nearly always allotted to Stephenson, we by no means detract from the high praise due by the world to the latter. Whatever may have been the improvements effected in the locomotive as a distinct mechanism, it never could have arrived at the height of its present efficiency as "a space and time annihilator," had not the improvements in the "iron way" been simultaneously effected. Without the improved system of rails introduced by Stephenson, the locomotive engine would have been comparatively useless; and without the speed attained by the improved locomotive, the improved system of rails would have been so commercially unremunerative as to have been altogether set aside. These were the elements of high velocity, "each of which formed the absolute condition of the existence of the other." 66 I am, I think, safe in saying," remarks Mr. Scott Russell, in his eulogium on George Stephenson, "that the wrought-iron railroad (Stephenson's) was essentially dependent on the locomotive engine. But that the modern locomotive engine could not subsist without the wrought-iron rail, and its multifarious appendages of chains, keys, locks, sleepers, switches, crossings, sidings, and turn-tables, is too evident to need proof. Without the smoothness of the rail, the engine would be jolted to pieces; and without the easy motion which it gives, the engine could not be made to draw a sufficiently profitable load to pay; and further, unless made of wrought-iron, it would be impossible to attain the high speed of the locomotive without imminent danger. It therefore appears, that the continuous wrought-iron railway and the locomotive engine were inventions intimately related to each other, and each a condition of each other's success. To Stephenson we are indebted for the chief features of improvement in both. It was the joint perfection of the road and the engine which created the Liverpool and Manchester line, and all the progeny of that wonderful and gigantic experiment, an experiment whose complete success now bears incontrovertible testimony to the genius of the man." Historical evidence, recently made public, proves most decidedly that to the inventive genius of Timothy Hackworth the locomotive engine owed nearly all the improvements which made it an efficient machine; improvements, too, effected at a time "when every thing had to be learned,-when, indeed, engineers were utterly thrown upon their own resources." Those who are desirous to enter into an investigation of the

L

point, and to be made aware of the extent to which Stephenson was indebted to the ability and experience of Hackworth in locomotive mechanism, should read the article in the Practical Mechanic's Journal, p. 49, vol. iii. 1850-1, entitled "A Chapter in the History of Railway Locomotion," and the "Memoir," p. 225, same volume. We think that an unprejudiced perusal of these interesting papers will induce the reader to coincide with the opinions of the writer as therein expressed. "If George Stephenson deserved the title of the 'Father of Railways,' we think we may at least claim for Timothy Hackworth that of the 'Father of Locomotives.""

In 1814 George Stephenson constructed a locomotive, Lord Ravensworth, of the Killingworth Colliery, having assisted Stephenson with money to conduct his experiments. This was tried on a tram-way at Killingworth. In 1815, in conjunction with another party, he took out a patent for "various improvements in locomotives." In this engine two cylinders were used, one at each end; the connecting-rods were attached to pins on a spoke of the wheels; they were placed at right angles to each other; by this means the motion was rendered continuous, one crank or pin receiving the full leverage of the connecting-rod while the other was at its dead point. A toothed wheel was placed on each axle inside the wheels, and round the two wheels a peculiar kind of endless chain was stretched

n

οι

(see p. 50, Mechanics and Mechanism); this chain was so constructed as to furnish a series of rectangular apertures, into which the cogs in the toothed wheels entered; by this arrangement, as the wheels revolved the chain was passed along, and one wheel could not revolve without the other; the relative positions of the cranks or pins (namely at right angles) was thus preserved. In the year 1816 he took a patent, in conjunction with Mr. Losh, which embodied many of his notable improvements in the construction of railways. In this patent one claim having reference to the construction of locomotives was included; this was a very ingenious method of "sustaining the weight, or part of the weight, of the engine upon pistons movable within cylinders, into which the steam or the water of the boiler is allowed to enter, in order to press upon such pistons, and which pistons are, by the intervention of levers and connecting-rods, made to bear upon the axles of the wheels of the carriage upon which the engine rests." In fig. 140 we give a transverse section, exhibiting the improvements here mentioned, and the arrangement of the, parts of the engine at this period. The boiler is at n n; b, the internal furnace; c, the flue or chimney; d, the cylinder; e, the

m

fig. 140.

m