RAILWAY MACHINERY

WHEELED OR ROLLING PLANT

LOCOMOTIVES

HISTORICAL PROGRESS OF THE LOCOMOTIVE

By Daniel Kinnear Clark, C.E.

CHAPTER I

GENERAL HISTORY OF THE LOCOMOTIVE, FROM 1784 TILL 1830

 It would probably be deemed an inconsistency, in a work professedly on the mechanism of railways, were nothing to be told of the doings of the 'fathers' of locomotion. The fathers are numerous, and the family have been innumerable; yet the whole matter is substantially of recent origin - being virtually comprised within the limits of half a century. Locomotives, though a recent, are already an honourable progeny; and their importance has imparted some vigour to the rivalry with which antagonistic claims have been supported, which renders the subject one of considerable confusion, and, we may add, of considerable delicacy. Altogether, the story of the locomotive wears an artificial aspect of antiquity, conferred equally by the scantiness of the published materials which have been handed down to us by the preceding generation, and by the difficulty of estimating relative merits where all have been indisputably of essential service, and many have remained unobtrusive, and their labours comparatively forgotten or unknown.

It is well understood that railways owe their origin to the necessities of the trade in coal, and that they were in operation in England as early as 1650. The rails, originally of timber simply, were, in 1760, shod with iron, for durability. In 1767, rails, entirely of cast-iron, were introduced at Coalbrookdale; and in 1805, rails formed of wrought-iron bars were laid down in the neighbourhood of Newcastle.

Solid wrought-iron, though employed so early as 1805, in the manufacture of rails, obtained but little consideration till 1820, when rails were formed in fifteen-feet lengths, of the 'fish-belly' form, which ultimately became extensively patronized. Soon after the introduction of the fish-belly rail, it was rivalled by the parallel rail, of uniform depth throughout, and was finally superseded by it.

The introduction and improvement of the locomotive followed gradually upon the improvements that had been made in the permanent way. The first suggestion of the locomotive is due to the illustrious Watt. So early as 1759, he suggested, to the late Dr. Robison, the application of the power of the steam-engine to the propulsion of wheeled carriages. The locomotive-carriage is also described in bis patent of 1784. Watt, however, relinquished the idea, as he had no feeling for high-pressure steam; and the improvement of the steam-engine by condensation appears wholly to have engaged the mechanical genius of his time. Watt's sympathies were naturally in favour of his pet condenser; and though, centuries before he was born; it had been agreed that 'nature abhors vacuums,' it is certain that Watt loved nothing better.

Watt's friend and assistant, William Murdoch, took up the idea of the ateam-carriage broached by his patron, and constructed a non-condensing steam locomotive of lilliputian dimensions, in the year 1784, the date of Watt's second patent. This locomotive, placed on three wheels, is shown in

Fig. 1

Murdoch's Locomotive, 1784 - Cylinder ¾ by 2 inches; Wheel, 9½ inches

Fig. 1. The boiler is of copper ; the flue passes obliquely through it, and is heated by a spirit lamp. The cylinder is ¾ inch diameter, and has 2 inches stroke: it is fixed on the top of the boiler, and the piston-rod is connected to one end of a vibrating beam, to which also is attached the connecting-rod for working the crank of the driving axle. The slide-valve is double-cylindrical and worked directly by the beam, which strikes the shoulders of the valve-spindle; and the exhaust steam passes through the hollow of the spindle, going out near the top. One of the wheels only is fixed on the crank-axle, and a single wheel is placed in front, working in a swivel frame, to allow the carriage to ran in a small circle. The driving-wheels are 9½ inches diameter, and the leading-wheel 4¾ inches. Notwithstanding these diminutive dimensions, this little gentleman managed to outrun the inventor, on one occasion. 'One night, after returning from his duties at the mine,' in Redruth, Cornwall, where he resided for some time, in charge of the mining engines, 'he wished to put to the test the power of his engine; and, as railroads were then unknown, he had recourse to the walk leading to the church, situated about a mile from the town. This was rather narrow, but kept rolled like a garden-walk, and bounded on each side by high hedges. The night was dark, and he alone sallied out with his engine, lighted the fire or lamp under the boiler, and off started the locomotive, with the inventor in full chase after it. Shortly after, he heard distant, despair-like shouting; it was too dark to perceive objects, but he soon found that the cries for assistance proceeded from the worthy pastor, who, going into town on business, was met on this lonely road by the fiery monster, whom he subsequently declared he took to be the Evil One in propria persona.

It is to Richard Trevethick that the world is indebted for the introduction of the steam-engine on railways, acting solely by the expansive force of steam. In 1802, he, in conjunction with Vivian, patented the application of the non-condensing engine to propel carriages on railroads. It was obvious that lightness and portability were indispensable to any successful attempt at locomotion, and he, like Murdoch, at once adopted the high-pressure principle. The first steam-carriage made by Trevethick was tried on common roads. It resembled in form the ordinary stage coaches, having two small wheels in front, by which it was guided, and two larger ones behind, by which it was driven. It had but one cylinder, placed horizontal, and this, together with th« boiler and fire, which were all enclosed in a cover, was situated low down in the rear of the hind axle. The motion of the piston was transmitted to a separate crankaxle, from which, through the medium of spur-gear, the axle of the driving-wheel derived its motion. The wheel-axle was mounted with a fly, to equalize the motion, and to offer brake surface down hill. The steam-cocks were worked off the crank-axle, as were also the force-pump, and the bellows for quickening combustion. In this engine may be recognized the horizontal inside cylinder, and the separate crank-axle, concerning which some discussion has arisen in later times.

In 1804, Mr. Trevethick patented and made a second engine in South Wales, to run upon the Merthyr-Tydvil Railway. It had a cylindricaI boiler with flat ends, since called by his name. The furnace and flue were inside the boiler, the latter recurving and leaving the boiler at the fire-door end; the cylinder was 8 inches diameter, had 4½ feet stroke, and was immersed upright in the boiler. The waste steam was thrown into the chimney, The wheels were plain, and found to have ample adhesion. The engine drew 10 tons of bar iron, besides the waggons, at 5 miles per hour, for a distance of 9 miles, carrying with it sufficient water and fuel for the trip. The variable nature of the adhesion between the driving-wheels and the rails, which, no doubt, occasionally manifested itself, led Mr. Trevethick to suggest auxiliary means of propulsion. Following up the presumed necessity. Mr. Blenkinsop, of Middleton Colliery, Leeds, patented, in 1811, the application of a rack laid alongside the railway, which was geared into by suitable spur-wheels driven by the engine, and which would thereby effectually insure a regular progressive motion. This patent was at work for some years, and in the engine adapted with the gearing, two cylinders were employed, let into the boiler vertically, working, by suitable cross-heads and connecting-rods, separate shafts under the boiler. The cranks of the one shaft moved at right angles with those of the other. Each shaft carried a spur-wheel, which geared with an intermediate wheel on the shaft of the driving spur-wheel. The engine ran on four plain flanged wheels, unconnected with the propelling apparatus. By the use of this rack-rail, the engine ascended gradients inaccessible to Trevethick's engine.

The weight of Blenkinsop's engine was said to be five tons, its evaporation 8 cubic feet of water per hoar, with a consumption of 75 lbs. of coal; it conveyed 94 tons on a level, at 3½ miles per hour, or 15 tons up a gradient of 1 in 15; maximum speed, 10 miles per hour.

The rack-rail was not discontinued until, by an improved distribution of the load on the wheels, it was proved by Blackett that the simple adhesion was sufficient. The most important feature of originality in Blenkinsop's engine is the employment of two cylinders, working alternately into the same shaft. Certainty of starting, and uniformity of motion, were thereby obtained, and to this day equivalent means for that purpose are employed.

The next in the list of devices for procuring a fulcrum is a scheme - patented, of course - by the brothers Chapman, in the end of 1812. These worthies applied a chain extending the entire length of the rails, coiled once round a grooved wheel carried and driven by the locomotive. The wheel being turned, it found its way along the chain, which was firmly fixed at the extremities, and progressive motion was so obtained. An engine of this kind was tried on the Hetton Railway, near Newcastle.

But invention was busy with locomotives. Brunton, of Butterly Works, if he could not produce a better thing, at least brought out something original in 1813. He applied automaton legs to the hinder part of the engine, which were worked by a species of parallel motion, off the cylinders, of which there was a pair, placed horizontally on the end of the boiler. These legs, 'imitations of nature,' were to be the means of propulsion.

The current of invention in search of an independent fulcrum was arrested by the good sense and perseverance of Mr. Blackett. of the Wylam Railway. He had, about this time, considerably improved his engines, and, by experiments, had ascertained the amount of adhesion of wheels on the rails. He found that the weight of the engine, duly distributed on the wheels, was sufficient to drag, with ordinary certainty, a requisite number of loaded waggons. The sufficiency of the superficial adhesion or bite having been established, general attention was re-directed to the means of applying the steam power to the wheels. Double- cylinder engines were now exclusively employed, as the cylinders, working alternately, afforded, in all positions of the engine, available power for starting, and for maintaining a uniform motion.

Early in 1814, an engine was constructed at Killingworth Colliery by George Stephenson, and, in the middle of the year, was set to work. This engine had a cylindrical boiler, 34 inches diameter and 8 feet long, with an internal flue-tube, 20 inches diameter, passing through the boiler. It had two vertical cylinders, let into the boiler, 8 inches diameter and 2 feet stroke, working, with cross-heads and connecting-rods, the propelling gear. The peculiarity of this engine was the mode of turning the wheels - a modification of Blenkinsop's gear. The engine was carried on four wheels of equal diameter; the two axles were mounted each with a 24-inch spur-wheel; three 12-inch spur-wheels were disposed on the horizontal centre line of the axles,
Fig. 2

Stephenson's Locomotive - Driving Gear, 1814

gearing into each other, and into those on the axles, forming a series of five working together. The connecting-rods were attached to cranks on the axles of the outer 12-inch wheels, from which the power was transmitted to the driving-wheels. The middle wheel operated as a regulator in preserving the two cranks at right angles, and in equalizing the propelling power. It is obvious, too, that the cranks made two revolutions for one of the wheels. This engine was tried on an incline of 1 in 450; it dragged 8 loaded carriages, about 30 tons gross weight, at 4 miles per hour; and continued regularly at work. The spur- wheel motion caused considerable noise and jarring, which increased with the wear. To remedy this, Mr. Stephenson, in conjunction with Mr. Dodds, patented, in 1815, a mode of driving the wheels directly by crank-pins, fixed in the arms of the wheels, one pair of wheels to each cylinder; crank-pins were caused to work square with each other, by means of an endless chain, working round wheels fitted with cogs to receive the links. It had a third pair of wheels, between the two extreme pairs, which also was moved by the chain. This contrivance superseded the use of spur- gear, and worked well.

Experiments for stimulating the draught of the furnaces were not wanting, great height of chimney being of course inadmissible. Trevethick employed bellows for that purpose, in his first engine; in his second, made in 1804, he turned the waste steam into the chimney. Many years afterwards, in 1815, he proposed two modes of aiding the draught mechanically; first, by fanners, which were to operate by blowing the fire; secondly, by a screw or set of vanes placed in the flue. The first proposal of fanners employed in this way is, however, due to the Chapmans, who embraced it in their patent of 1812. None of these modes of obtaining artificial draught appear to have been at all generally employed. The truth is, that until 1825 nothing but slow speeds were ever contemplated by those engaged in the manufacture of engines; and the unassisted evaporative power of the boiler of the old engines was, in general, competent to the production of at least as much steam as could do the work of seven or eight horses. This was, of itself, considered an achievement; and it seems to have contented mechanical men interested with railways, for a quarter of a century.

The locomotive remained, for many years, very much in the condition to which it was brought by Stephenson in 1814. In matters of detail, outside coupling-rods were substituted by Stephenson for chains, to connect the driving- wheels on the engines of the Killingworth Railway; and steel bearing-springs were interposed over the axle-boxes. Mr. Nicholas Wood, also, added wrought-iron tyres to the driving-wheels. On the Wylam Railway, the engines employed in 1825 were, in consequence of their extreme weight, placed on eight wheels, disposed in two groups of four, each of which was arranged under a distinct frame or 'bogie.' The total load being so placed on two frames connected by swivelling joints to the principal frame, not only was the load widely distributed upon the rails, the wheels were also enabled, notwithstanding the extended base which they presented, to pass round sharp curves with freedom. This was the first application of the bogie-frame system, though it had been proposed long previously by the Chapmans, who described it in their patent of 1812. In 1827, Mr. Timothy Hackworth, manager of the Stockton and Darlington Railway, applied the blast-pipe in the chimney to an engine, the Royal George, constructed for that line, and re-arranged by him. This is said to have been the first efficient application of the blast-pipe as a promoter of combustion. This engine, designed for coal traffic, had 6 wheels, of 4 feet diameter, four of them being mounted with bearing-springs, and was the earliest of the six-coupled wheel class. The cylinders, 11 inches by 20 inches stroke, were placed vertically over the leading-wheels, and fixed to the smoke-box. The boiler was cylindrical, 4 feet 4 inches in diameter, and 13 feet long. It contained an internal tube, which carried the fire-grate, bent double into a horse-shoe form, 26 and 18 inches diameter, at the furnace and chimney ends respectively. Thus the chimney, a mere continuation of the flue, was situated at the furnace end of the boiler; and the return of the tube yielded twice the ordinary heating surface of the locomotives of this period; as in these the tube passed but once through the boiler. In this locomotive, a cistern was attached to the smoke-bos, into which the waste steam could be turned, for heating the feed-water: here also the short-stroke pump was first employed, being driven by the eccentrics, and spring balances for the safety- valves, in place of weights. This engine was capable of conveying 24 waggons of coal - 100 tons gross weight - at a regular speed of 5 miles per hour, and it frequently travelled with its load at 9 miles per hour. The useful loads were, on this line, conveyed in the descending direction, from the pits. In ascending, on the return trips, the locomotive usually conveyed 30 empty waggons, each 80 cwt., making a total load of 45 tons, on gradients varying from 1 in 100 to 1 in 500.

The general arrangement of the old Killingworth locomotive, as it existed previously to 1829, is represented by the annexed figure. The boiler was of wrought iron, cylindrical,
Fig. 3

Killingworth Railway Locomotive, previous to 1829

with flat round ends, 9 feet long, 4 feet diameter; a cylindrical tube, 22 inches diameter, passed through the boiler, two inches clear of the bottom. The fire-grate was placed in one end of the tube, 4 feet long. The other end terminated in the chimney. The boiler rested on a timber frame, with springs interposed. The wheels were 4 feet diameter, coupled. There were two cylinders let vertically into the boiler, each working its own pair of wheels, alternately with the other. The exhaust steam was thrown into the chimney, in compliance with a suggestion of the elder Stephenson''s, previous to 1825, though the blast was not considered to be an essential feature. Indeed, Mr. Wood, writing in 1825, regarded the blast as 'an accidental circumstance,' and though it promoted evaporation, it wasted fuel, and he superseded it by an enlargement of the flue-tubes, and consequently of their heating surface. The engine was provided with a tender, carrying fuel and water. The maximum performance of this engine, weighting 6½ tons, and with tender, fuel, and water, 10 tons, was equal to 50 tons gross load, including engine and tender, on a level, at 6 miles per hour; the evaporation being 15 cubic feet of water per hour. This was the average performance of the engines on several other railways about the same time, as we find from the report of Messrs. Walker and Eastrick to the Liverpool and Manchester Railway Company, published in 1829, that an engine weighing, with tender, 10½ tons, was capable of conveying a load of 19½ tons, or, including engine and tender, 30 tons, at 10 miles per hour on a level, equivalent to 300 tons conveyed 1 mile per hour, which is also the duty of the Killingworth engine, as 50 X 6 = 300 tons, 1 mile per hour.

The opening of the Stockton and Darlington, in 1825, as a passenger railway, and the improvements effected in the locomotives by Mr. Hackworth, created a taste for high speeds. This feeling rendered it imperative to have light, solid, and powerful engines. So much did the feeling prevail about the time of the opening of the Liverpool and Manchester Railway, in 1829, that the directors, for want of locomotives possessed of the necessary qualities, seriously contemplated the employment of stationary engines to work the traffic of their 30-mile railway.

It was reserved for our French neighbours to work out the problem. The introduction into France of the imperfect locomotive of the time - imperfect so far as high speeds were desirable - led to the solution of the question of light and powerful engines. 'The first locomotives, two in number, that were sent to France,' says M. Lobet, 'were made by George Stephenson, and arrived there in 1829, for the Lyons and St. Etienne Railway, of which M. Seguin was the engineer. On trial, their mean velocity did not exceed 4 miles per hour. To increase the efficiency of his engines, M. Seguin felt the necessity of increasing their evaporating power, and resolved to apply a scheme of his own to the engines he was about to construct (on the model of Stephenson's) - a scheme which he had cherished since 1827 (and had patented in February 1828), and which consisted in multiplying the heating surface, by subdividing the current of hot air into streamlets, which flowed through a series of tubes immersed in the water of the boiler. The method of the tubes increased amazingly the heating surface, and with it the evaporative power, and it is precisely to this evaporation that we are indebted for speeds which before were thought impossible. But another difficulty presented itself; the height of the chimney, necessarily limited, was incompetent to maintain the draft, the resistance of which was so much increased by the increase of surface in the new boiler. M. Seguin, therefore, added a circular fan for promoting the draft, and it was partially successful. M. Pelletan, however, completed the solution of the problem, by suggesting the steam jet in the chimney; and, as usual, England appropriated the invention of the two French engineers.

The suggestion and application of the subdivided tube surface is, by common consent, ascribed to M. Seguin. The steam-jet in the chimney, though no doubt invented independently by Pelletan, had been, as we have seen, previously applied by Stephenson and Hackworth. It was however, at the same time, but partially employed in this country, as we may infer from the absence of the jet in the sample engines sent to France. The method of the multi-tubular flue and the steam-jet are parts of one system; they co-exist as naturally as the condenser and air-pump of Watt's engine. The locomotive was not ripe for the application of the blast pipe; the large and vacuous cavity of the flue-tube, while it presented a very restricted area of heating surface, permitted great freedom of circulation, and the greater length and surface of Hackworth's doubled flue, enabled him, on this account probably, to employ the blast with greater success than had been done by his predecessors. Again, the tubes of M. Seguin, while they increased the heating surface, increased the friction surface of the flue way simultaneously; and here it was that the aid of mechanical expedients became more than ever necessary, to uphold the requisite rate of combustion. The method of the steam blast, therefore, of spontaneous invention at home, was in France the child of necessity. The tubes formed the link between the fire-box and the jet, and thus the problem of producing a light and powerful locomotive was solved.

It was determined by the directors of the Liverpool and Manchester Railway, irrespective of what had been doing in France, of which probably they were unaware, to offer a premium for the best locomotive engine, which should draw, on a level plane, three times its own weight, at 10 miles per hour. The trial was to take place on a 1½ mile stage, with one-eighth of a mile extra at each end for starting and stopping, and to consist of twenty double trips. The engine was to consume its own smoke, the whole weight of the engine and boiler to be carried upon springs, and should the weight have exceeded 4½ tons, the engine was to have six wheels. From this time, 1829, may be dated the era of modern locomotives in England.

Three locomotives were put in for competition, viz.:-
Engine
Maker
Rocket Robert Stephenson, of Newcastle
Sanspareil Timothy Hackworth, of Shildon
Novelty Braithwaite and Ericson, of London

The Rocket was the first locomotive made in England

Fig. 4

R. Stephenson's Locomotive - The Rocket, 1829

with multitubular flues. The tubes were adopted at the suggestion of Mr. Booth of the Liverpool and Manchester Railway, to whom the merit of their invention in this country is commonly ascribed. The boiler was cylindrical, with flat ends, 6 feet long, and 3 feet 4 inches diameter; the firebox, in the rear of the engine, was 2 feet long, 3 feet broad, and 3 feet deep, inside measure, and was surrounded on the two sides, the front, and the top, by an external case, affording a 3 inch water-space. The flue consisted

Fig. 5

Rocket - Section of Boiler

of 25 tubes, 3 inches diameter; the cylinders, two in number, placed obliquely next the fire-box, and working the fore-wheels, were 8 by 16½ inches stroke; driving-wheels 4 feet 8½ inches diameter; the exhaust pipes were originally arranged to deliver the steam directly from the cylinders into the atmosphere, under the impression, no doubt, that the abundance of heating surface, unaided, would have commanded an abundance of steam. After some preliminary trials, however, previous to the commencement of the competition, during which the superior evaporating power of the Sanspareil, with a sharp blast from the exhaust directed upwards into its chimney, became apparent, it was resolved to discharge the exhaust steam of the Rocket into the chimney; and on the eve of the first day of the trial, the exhaust pipes were diverted into the chimney with an upward termination. The fire-grate surface was 6 feet; fire-box surface, 20 feet; tube surface, 117.75 feet.

The Sanspareil had a cylindrical boiler 4 feet 2 inches diameter, and 6 feet long. The grate and chimney were

Fig. 6

Hackworth's Locomotive - The Sanspareil, 1829

situated at one end of the boiler, and connected by a single flue-tube, with one bend, 24 inches diameter at the grate, and 15 inches at the chimney. The grate was 5 feet long by 2 feet broad, and was overhung by the boiler, by the addition of semicircular water-chambers. The steam was thrown into the chimney to stimulate the draft, by means of the blast pipe already applied to the Royal George. The violence of the draft so produced, became very evident during the experiments. The two cylinders, 7 by 18 inches stroke,

Fig. 7

Sansparell - Boiler

were placed vertically over one pair of wheels, and the four wheels were 4½ feet diameter, coupled. The grate surface was 10 feet; fire-box surface, 15.7 feet; and tube surface, 74.6 feet.

The Novelty was peculiarly constructed; the fire-box was, like that of the Eocket, placed at one end, enveloped in the

Fig. 8

Braithwaite's Locomotive - Novelty, 1829

water of the boiler; it was 18 inches diameter, close at the bottom, and fed through an air-tight hopper. The flue was a single tube, 4 inches diameter at the fire-box, 3 inches at

Fig. 9

Novelty - Boiler

the chimney, and 36 feet long, traversing the boiler three times. The fire was urged by bellows, situated near the chimney. The engine had but one cylinder, 6 by 12 inches stroke, placed vertically, and driving one pair of wheels 4½ feet diameter, by means of bell-cranks; the steam was exhausted directly into the atmosphere. Grate surface, I.8 feet; fire-box surface, 9.5 feet; tube surface, 33 feet.

The respective weights of the three engines and their load^ in working order were as follows:-

Rocket          
tons
cwt.
qrs.
lbs.
  Engine weight        
4
5
0
0
   
tons
cwt.
qrs.
lbs.
        
  Tender
3
4
0
2
        
  Two loaded carriages
__9
_10
__3
_26
        
  Drawn weight        
_12
_15
__0
__0
  Total weight of Train        
_17
__0
__0
__0
 
Sanspareil          
tons
cwt.
qrs.
lbs.
  Engine weight        
4
15
2
0
   
tons
cwt.
qrs.
lbs.
        
  Tender
3
6
3
0
        
  Two loaded carriages
_10
_19
__3
__0
        
  Drawn weight        
_14
__6
__2
__0
  Total weight of Train        
_19
__2
__0
__0
 
Novelty          
tons
cwt.
qrs.
lbs.
  Engine weight, exclusive of tank        
3
1
0
0
   
tons
cwt.
qrs.
lbs.
        
  Tank, loaded
0
16
0
14
        
  Two loaded carriages
__6
_17
__0
__0
        
  Drawn weight        
__7
_13
__0
_14
  Total weight of Train        
_10
_14
__0
_14

The drawn weights attached to the Rocket and the Sanspareil were the regulation loads, three times the weight of the engine. As the Novelty had no tender, the same carrying-weight was assigned to it, in proportion to the exclusive weight of the engine, that existed in the experiment with the Rocket.

The Rocket was the only engine that accomplished the stipulated distance of 70 miles. Its average speed on the stage was 13.8 miles per hour; the greatest velocity, in any trip, was 29 miles per hour; the consumption of coke per mile, per ton of total load of train, was 0.91 lbs., and per cubic foot of water evaporated, 11.7 lbs.; the evaporation, 18.24 cubic feet of water per hour.

The Sanspareil ran a distance of 27.5 miles; average speed, 14 miles; greatest speed, 22.6 miles; consumption of coke per mile, per ton of total load, 2.41 lbs., and per foot of water evaporated, 28.8 lbs.; evaporation, 24 feet of water per hour.

The Novelty, by a series of unfortunate accidents, failed twice in the midst of the experiments. The engine, with its load, traversed the stage at 15 miles per hour.

After these trials, the orifice of the exhaust tube of the Rocket was contracted, to sharpen the blast, and promote the evaporation. On trial, the engine evaporated 29.6 feet of water, and conveyed an average load of 40 tons at 13.3 miles per hour, with steam at 50 lbs. No notes of the consumption of fuel were taken.

The Novelty also underwent considerable alterations; amongst others, a separate cylinder was applied for working the bellows. At a subsequent trial on the experimental stage, the engine conveyed a total average load, its own weight included, of 28.5 tons, at an average speed, on the stage, of 8 miles per hour. The coke consumed per hour was 84 lbs., during 6¼ hours, the bellows being at work during the whole of that time. The consumption was, therefore, equivalent to 0.36 lbs. per ton per mile.

The advantage of extended flue surface having been established, the boiler of one of the old Killingworth engines was altered by Mr. Nicholas Wood, and fitted with tubular flues to the following dimensions:— boiler, 9 feet 2 inches long, and 4 feet in diameter; elliptical tube, within which the fire was placed, 28 by 24 inches high, and 4 feet 8 inches long; grate surface, 10.9 feet; fire-box surface, 22'56 feet; forty- three tubes, 2 inches diameter, and 4½ feet long; 301.5 feet of surface; sectional area of tubes, 185 inches. With a total load of 70.5 tons, including engine and tender, the speed attained on a level was 9 miles; the evaporation was 47.8 feet of water per hour, with a consumption of 14.7 lbs. of coal per foot of water. By another experiment, with a total load of 40 tons, at a speed of 9 miles, the evaporation was 40 feet of water per hour, with 13.2 lbs. of coal per foot. In both of these experiments, the steam was blowing off at the valve.

Experiments were made by Mr. Stephenson on two new engines constructed on the principles of the Rocket, namely, the Phoenix and the Arrow, with a much more extended flue surface. These engines had, respectively, 90 and 92 tubes, 2 inches diameter; their boilers were 3 feet diameter, and, respectively, 6½ and 6 feet long; grate surface of both, 6 feet; fire-box surface, 20 feet; tube surfaces, 306.0 and 283.8 feet respectively.

The Phoenix had two cylinders, 11 inches diameter, by 16 inches stroke; and was carried on four wheels, of which the driving-wheels were 5 feet in diameter, and the carrying-wheels 2 feet 8 inches diameter. The Arrow's cylinders were 10 by 16 inches; driving-wheels 5 feet diameter, and carrying-wheels 2 feet 8 inches diameter.

The average results of the trials are placed in the following Table, in which the experiments previously detailed are reduced, and classified for comparison:—

In the Table it appears that while the old Killingworth engine moved a total load, including itself, of 50 tons, at 6 miles per hour, the Rocket, when altered, moved 47.45 tons at 13.3 miles per hour; subtracting the weights of engine and tender, the work done was 40 tons at 6 miles, and 40 tons at 13.3 miles. Thus the Rocket, which was 25 per cent. lighter than the old Killingworth, did more than double work. The evaporation of the Rocket, moreover, was nearly double that of the old engine, being as 29.6 to 16 feet of water per hour-a superiority owing jointly to the greater heating surface, and to the sharper blast of the Rocket, notwithstanding its smaller grate surface. How much depended on the blast, may be found from the relative evaporations of the Rocket before and after the alteration, which were 18.24 and 29.6 feet of water per hour. In comparing the Rocket, as first tried, with the old engine, though their relative evaporations were 18.24 and 16 feet of water, the performance of the former was the inferior, being equivalent to 138 tons at 1 mile per hour, while that of the other was 150 tons at 1 mile-a difference attributable, partially to the absorption of a portion of power in the exhausting action of the blast of the Rocket, and partially to the escape of a greater amount of unemployed heat by the chimney. It is remarkable that the two evaporations should be so nearly the same, when the heating surfaces are, in slump, so various as 41 and 138 feet. This is explained by the deficient energy of the blast, in the Rocket, to maintain the draft against the extensive frictional tube-surface, and through a sectional area of flue little more than one-third that of the old engine. With the easy blast, nevertheless, the heat of the fuel was permitted to be more thoroughly extracted, in the ratio of 11.7 lbs. of coke per foot of water evaporated by the Rocket, to 18.34 lbs. of coal by the old engine.

The consumption of fuel by the Sanspareil was extrava- gant. This was due to a special imperfection in one of the cylinders which had been imperfectly cast, and had been reduced at one place by boring to 1/16 inch thick. The engine had no sooner commenced working than one cylinder burst, when the race had to be run with one perfect cylinder only; whilst the fracture of the other one opened at every stroke a direct communication between the boiler and the blast-pipe. The fuel was thus dragged from the fire-box in solid pieces, and was blown unconsumed through the chimney-a result which sufficiently explained the inferior economy of fuel per foot of water evaporated, com- pared even with the old engine; the consumptions being, respectively, 28.8 and 18.34 lbs.; though the proportions of the boiler surface of the Sanspareil are superior.

In the Killingworth new engine, with a heating surface three times that of the old engine, and a grate surface fully one-half greater, there is in one experiment three times the evaporation, with less consumption of fuel per foot of water, though the consumption per mile per ton is greater. This proves the efficiency of extended heating surface for purposes of evaporation; it proves too that superior evaporation was obtained at the cost of steam power in the blast, which resulted in a greater consumption of fuel per ton per mile. But this increased consumption was due not merely to increase of frictional surface, in the ratio of 1 to 3½, but also to a diminution of sectional area of flue, in the ratio of 3 to 1, nearly.

The experiments with the Novelty are remarkable. This engine was proved, when fairly tried, to have consumed less than half the fuel per ton per mile required by the Rocket, notwithstanding the closeness and contracted sectional area of the flue of the Novelty, which was but one twenty- fifth of that of either of the other competing engines. The mode of stimulating combustion by compression, adopted in the Novelty, was, no doubt, the source of the economy, in conjunction with the very much greater proportion of heating surface to the area of grate, especially when intensity of action was essential.

We need not longer dwell over these rudimentary experiments. They have suited the purpose of exemplifying generally the nature of the considerations to be regarded in the composition of the locomotive engine. The experiments indicated plainly in what directions improvement was to be hoped for. The steam-blast permitted the use of coke as fuel, with excellent effect; and from the time of the trials of 1829, may be dated the general use of coke as fuel, in preference to raw coal, as it showed less flame, threw off less smoke, and imparted quite as much heat per unit of weight. While the Rocket had twenty-four tubes of 3 inches diameter, the Meteor had eighty tubes of 2 inches diameter; and the Comet, the Dart, and the Arrow, ninety 2-inch tubes. The boilers of these four last engines, which were made, soon after the Rocket, for the Liverpool and Manchester Railway, were not greater in lineal dimensions. being 3 feet diameter by 6 feet long; the cylinders, however, in virtue of the greater evaporation, were made 10 inches in diameter, 16-inch stroke, with 5-feet wheels. In the Northumbrian, and other succeeding engines, 1.625 inch tubes were introduced, the boiler was lengthened 6 inches, and the cylinders were made 11 inches in diameter.

The first eight engines made by Mr. B. Stephenson for the Liverpool and Manchester Railway, including those just noticed, were made on one general plan: 4-wheel engines, tall and square, with outside cylinders in an inclined position, and working on crank pins fixed to the driving-wheel. These engines, from their shortness, and from the extreme transverse distance of the cylinders, were susceptible at high speeds of a violent oscillatory motion, which eventually led to their abandonment.

While Mr. Stephenson was carrying out the perfections in the detail of his locomotive-boilers, Hackworth was equally busy on the Stockton Railway. He designed a locomotive, the 'Globe,' built by Messrs. Stephenson &s Co., previous to 1830, comprising the following modifications. The wheels were four in number, and coupled, 5 feet in diameter, being the largest then in use. A single straight flue passed through the boiler, containing the fire-grate at one end. A series of small water-tubes were inserted as heating surface diametrically across the flue, in a spiral order, through which the water of the boiler circulated. A copper dome was placed on the top of the boiler, as a steam chamber, whence the name of the locomotive. The cylinders were placed beneath the boiler, and inside the wheels, along- side of each other; and worked the driving-axle direct. which was for that purpose fitted with two inside cranks at right angles, The valve-gear was reversed by a single lever, two drivers being placed on the axle, one on each side of the pair of eccentrics. The water-tabes, borrowed from Perkins's boiler, though they increased the heating surface, were speedily destroyed by the accumulation of mud in them, particularly those which lay horizontally. The Globe, nevertheless, frequently attained, it is said, a speed of 50 miles per hour.

In 1830, Mr. Hackworth designed two new classes of locomotives, to meet the increase of traffic on the Stockton line. In these he introduced two varieties of compound flue, the first of which comprised an arrangement the same as that already described for the new Killingworth locomotive, and from which probably Mr. Wood derived the idea. The second form of boiler contained the 'return multitubular fire-tube,' a single flue was passed right through the boiler, and discharged its contents into an intermediate smoke-box, whence a number of small tubes, returning through the boiler, conveyed the smoke to the fire-box end into the terminal smoke-box, whence it was discharged into the chimney. The second plan of boiler proved to be the best of its day for the general traffic of the line, both as to economy and durability; the flues have frequently been found to endure six rears without removal. In the same locomotives, the cylinders were placed vertically at one end of the boiler, and the pistons were coupled to a separate crank- shaft, hung directly beneath, having two cranks on its extremities, at right angles to each other, and from which the. whole set of wheels were driven by coupling rods. The slide- valves were driven each by a single eccentric ; and the same eccentrics were employed to work the pumps.

The first engine made by Mr. Bury was the six-wheel engine Dreadnought, which was placed on the Liverpool and Manchester Railway on March 12,1830. It was too heavy for the rail?, and was on that account condemned. His next engine was the Liverpool, made for the same railway; it was made with inside horizontal cylinders, and double crank- axle; the cylinders were 12 by 18 inches; the wheels, four in number, were 6 feet diameter, coupled. This engine was placed on the rails on July 22, 1830. It was the first of a class which afterwards got extensively into use, and of which further notice is reserved for next chapter.

The Planet, which was the ninth engine built by Mr. Stephenson for the Liverpool and Manchester Railway, embraced some conspicuous improvements; it was the combination, in fact, of what had previously been known; the multitubular boiler, the blast pipe, the inside horizontal cylinders, which were placed inside the smoke-box, and the double crank-axle. This engine had 129 tubes, 1.625 inches diameter; and the boiler was 3 feet diameter, by 6½ feet long, yielding a heating surface of 37.25 feet for the firebox, and 370 for the tubes; the cylinders were 11 by 16 inches, and the four wheels 5 feet and 3 feet diameter; the weight of the engine, empty, was 8 tons; with coke and water, 9 tons; tender, with coke and water, 4 tons; making a total of 13 tons. The engine is said to have taken, on its first trial, on December 4, 1830, a train of 76 tons of goods and passengers from Liverpool to Manchester, in 2 hours 39 minutes, with a maximum velocity, on a level, of 15½ miles per hour, under the disadvantage of an adverse wind, and new machinery.

The success of the arrangements combined in the Planet, formed a new starting point for improvement. New locomotives were from that time formed on the model of the inside-cylinder engine, and the pattern was early imitated on other railways.

From the foregoing notices, it appears that no single individual in this country had, up till the year 1830, done so much for the improvement of the locomotive, and for its establishment as a permanent railway motor, as Mr. Timothy Hackworth. He first employed six coupled-wheel locomotives; he first applied the waste steam to heat the feedwater; he first employed the eccentrics to work the feedpumps, which, in many cases, is a matter of convenience; he substituted spring balances for weights to the safety valves; he schemed and first applied the steam-chamber in the boiler, a valuable auxiliary for obtaining dry steam; he first placed the cylinders beneath the boiler, and employed the double inside crank-axle, coupled directly to the pistons; and he also was the first to employ, in railway locomotives, a separate crank-shaft hung in bearings fixed to the frame. He claimed also the invention of the blast-pipe: though, taking his own dates, we have found that George Stephenson had applied it previously. But Trevethick appears to have the most unequivocal claim to the invention, if, indeed, it was not altogether a matter of accident; because he was at least the first who discharged the steam into the chimney, and it was at the time distinctly known that the blast improved the draft of his engine, as we find from some remarks by Gilbert, in the 12th volume of Nicholson's Journal, 1805.

The above extract is Chapter One of "Railway Machinery - A Treatise of the Mechanical Engineering of Railways", Published in 1855 by Blackie & Son.