The evolution of the steam locomotive (1803 to 1898)

The premier International Exhibition, which, as all the world well knows, was held in Hyde Park, London, 1851, brought together quite a respectable collection of railway appliances. The British exhibitors showed the following locomotives:—

• London and North Western Railway’s “Cornwall” and “Liverpool.”
• Great Western Railway’s “Lord of the Isles.”
• Hawthorne’s express, “Hawthorn.”
• Adams’ combined engine and carriage, “Ariel’s Girdle,”
• built by Wilson and Co., Leeds.
• England’s light locomotive, built by Fairbairn.
• Fairbairn’s tank engine.
• South Eastern Railway’s “Folkestone.”
• E. B. Wilson and Co.’s double boiler tank engine.

Several of these have been described in an earlier chapter, whilst details of other types (such as the “Lord of the Isles” type) have also been given, so that it is not necessary to describe such designs again. We have, however, to give particulars of Hawthorne’s express, Fairbairn’s tank, the “Folkestone,” and Wilson’s “double boiler” tank engine. The dimensions of the first are: cylinders, 16in. diameter, 22in. stroke; driving wheels, 6ft. 6in.; leading and trailing wheels, 3ft. 9in. diameter; heating surface of fire-box, including water bridge, 110 sq. ft.; tubes, 865.4 sq. ft. The tubes were of brass, of 2in. external diameter, and 158 in number.

The “Hawthorn” had inside cylinders and double sandwich frames, a raised fire-box, with an enclosed safety valve, no dome, but a perforated steam-pipe for the collection of the steam was provided. The engine was designed for running at 80 miles an hour; the special features of the engine being double-compensating beams for distributing the weight uniformly on all the wheels, equilibrium slide-valves, and an improved expansion link suspended from the slide-valve rods. Instead of fitting a spring to each wheel, two only were placed on each side of the engine between the wheels. These springs were inverted, and sustained by central straps attached to the framing. Their ends were connected by short links to the wrought-iron double-compensating beams placed longitudinally on each side of the engine, inside and beneath the framing.

The two inner contiguous ends of these beams were linked by a transverse pin to an eye at the bottom of the axle-box of the driving axle, whilst the opposite ends of the beams were respectively linked in a similar manner to eyes on the top of the leading and trailing axle-boxes. The action of these beams was obvious. By them a direct and simultaneous connection was given to all the axle bearings, and consequently a uniform pressure was always maintained on all the wheels, irrespective of irregularities on the permanent-way. The slide valves were placed on vertical faces in a single steam chest, located between the two cylinders. One slide-valve had a plate cast on its back, and the other had an open box cast on its back to receive a piston, which had its upper end parallel with the valve face. This piston was fitted steam-tight in the box, and its planed top bore against the face of the plate in working. By this arrangement the slides were relieved from half of the steam pressure; and to assist a free exhaust, a port was made in the back plate of one of the slides, so providing an additional exit for the spent steam by means of the piston and the exhaust ports of the opposite valve.

The expansion link was placed in such a position as to allow the bottom of the boiler to be quite near the axle. The link, instead of being fixed to the ends of the eccentric-rods, so as to rise and fall with them when the reversing lever was moved, was suspended from its centre, by an eye, from the end of the slide-valve spindle. This removed the weight of the link, etc., from off the reversing gear. The eccentric-rods were jointed to the opposite ends of the link slide-block, to secure steadiness and durability of the parts. It was claimed that this method of a fixed link-centre as fitted to the “Hawthorn” ensured a more correct action of the valves.

Wilson and Co., of the Railway Foundry, Leeds, exhibited a curious tank engine at the Exhibition of 1851, called the “Duplex,” in consequence of it being provided with two boilers. The idea of the designer was to obtain sufficient steam from an engine of light weight to haul a heavy train. The original drawings of this engine are still in the possession of Mr. David Joy, who designed it; and at first it was proposed to build the “Duplex” with three cylinders and six-coupled wheels, but afterwards fresh drawings were prepared, and it was from these latter ones that the engine was built. The two boilers were placed side by side, and these each measured 10ft. 6in. long by 1ft. 9in. diameter, and together contained 136 tubes of 1¾in. diameter, the heating surface of which was 694 sq. ft., that of the fire-box being 61 sq. ft., making a total of 755 sq. ft. The cylinders were outside, their diameter being 12½in., and the stroke 18in. The leading wheels were 3ft. 6in. diameter; the driving and trailing (coupled) 5ft. diameter. Some other dimensions were:—Total length, 24ft. 3in.; breadth, 5ft. 3in.; height from rail to top of chimney, 13ft. 6in.; weight, empty, only 16 tons, with fuel and water 19 tons 17 cwt. The capacity of tank was 520 gallons, sufficient for a journey of 25 miles; coke bunker, 42 cubic feet, equal to 26 bushels, or 15 cwt. The “Duplex” was sold to a Dutch railway after the Exhibition, and its further career is, therefore, unknown to those interested in it.

Fairbairn’s tank locomotive was of the “well” type, supported on six wheels, the driving pair being 5ft. diameter, and the L. and T. each 3ft. 6in. diameter. The cylinders were inside, measuring 10in. by 15in. stroke. The boiler was 8ft. long by 3ft. diameter, and contained 88 brass tubes of 2in. diameter. The heating surface amounted to 480 sq. ft. The internal fire-box was of copper, and measured 2ft. 5in. long, 3ft. wide, and 3ft. 5in. deep. The tank behind and under the foot-plate held 400 gallons of water. The coke consumption of this little engine was only 10lb. per mile with trains of six carriages, the weight in working order only 13 tons; and it may interest our readers to know that this diminutive locomotive was described as “a fair specimen of the heavier class of tank engine.

The engine calling for the greatest attention at the Exhibition of 1851 was the “Folkestone” (Fig. 61), exhibited by the South Eastern Railway. This was an engine built by R. Stephenson and Co., under one of Crampton’s patents, but the principal feature in its design was an intermediate driving axle, connected by means of outside cranks, and coupling-rods to the driving wheels, which were (under Crampton’s patent) behind the fire-box, the axle extending across the foot-plate. It will be well, perhaps, if we at this point reiterate the fact that the method of working locomotives by means of an intermediate crank-shaft was not introduced by Crampton, it having been used some years previously by W. B. Adams, not to mention some of the early Stockton and Darlington Railway engines, where the same arrangement was employed, but with vertical cylinders. Readers will, therefore, see it is incorrect to describe locomotives with this system of machinery as “Crampton’s patent,” although it is quite possible for a “Crampton patent” locomotive to be provided with an intermediate driving shaft, as was the case with the “Folkestone.”

Eight engines of this type were built by Stephenson and Co. for the South Eastern Railway, and were numbered 136 to 143, the first of which was named “Folkestone.” These engines were supported by six wheels, a group of four being arranged close together at the smoke-box end. Their diameter was 3ft. 6in. The driving wheels were 6ft. in diameter, the wheel base 16ft. These engines weighed 26¼ tons each, of which only 10 tons were on the driving wheels, the remainder of the weight being supported by the four leading wheels. The cylinders were inside, 15in. diameter, and the stroke 22in. The fire-box top was flush with the boiler barrel, the straight lines of which were unrelieved by a dome, but an encased safety valve was fixed near the back of the fire-box top. The boiler contained 184 tubes, of 2in. diameter and 11ft. in length.

The “Folkestone” ran its trial trip on Monday, March 31st, 1851, when Mr. McGregor, the chairman of the South Eastern Railway, Mr. R. Stephenson, the builder of the engine, Mr. Barlow, the South Eastern engineer, and Mr. Cudworth, the South Eastern locomotive superintendent, were present. From London Bridge to Redhill no great speed could be attained, as a Brighton train was in front; but beyond the latter station, and with a train of nine carriages, the 19½ miles to Tonbridge were covered in 19½ minutes, a maximum speed of 75 miles an hour being attained. After a short stop, the journey to Ashford was resumed, and that town was reached in 20½ minutes after leaving Tonbridge. The times and distances were as follow:—Redhill to Tonbridge, 19 miles 47 chains, start to stop in 19½ minutes; Tonbridge to Ashford, 26 miles 45 chains, start to stop in 20½ minutes, or at the rate of 78 miles an hour; the whole 46 miles 12 chains being covered in 40 minutes, running time, or, including the stop at Tonbridge, in 43 minutes. It must be remembered that the line between Redhill and Ashford is, perhaps, the most level and straight in England for so long a distance.

These eight engines did not prove very successful in general working, and they were afterwards rebuilt as four-coupled engines, an ordinary cranked axle with wheels being provided in place of the intermediate driving shaft.

It will not be out of place if we here mention eight “single” engines built by Sharp Bros. in 1851 for the South Eastern Railway, and numbered 144 to 151. The general dimensions were similar to the Cramptons, except that the wheel base was only 15ft., and that the heating surface was 1,150 sq. ft. The admission of the steam to the cylinders was controlled by a hand lever, with catch and notches, similar to and placed by the side of the ordinary reversing lever. Six eccentrics were on the driving axle, two of them working the pumps. The framing and springs of these engines were afterwards perpetuated by Cudworth in his later and better known types of South Eastern locomotives.

The locomotives of the despised “Eastern Counties,” that were designed about 1850 by Mr. J. V. Gooch, will now be concisely described. They were of three kinds—viz., “single” tanks, “single” express, and four-wheels-coupled tender engines. Of the tanks, three sizes were constructed, chiefly at the “Hudson Town” (or Stratford Works). The largest of these were provided with outside cylinders, 14in. diameter and 22in. stroke, the boiler being 10ft. 6in. long, and containing 164 tubes of 1³/₁₆th in. diameter. The leading and trailing wheels had outside bearings, the driving wheels being provided with inside bearings only. A steam dome was placed over the raised fire-box, and a screw-lever safety valve on the boiler barrel. The water was stored in two tanks, fixed between the frames, one below the boiler and the other beneath the foot-plate. These tank engines were known as the “250” class, and some of our readers may recollect that when Peto, Brassey and Betts leased the London, Tilbury and Southend Railway, engines of this design were used to work the traffic on that railway. We understand it is now 20 years since the last of them (No. 08) reached the final bourne of worn-out locomotives—the “scrap heap.”

The dimensions of the smallest class of these tanks (Fig. 62) were: Cylinders, 12in. diameter, 22in. stroke; boiler, 10ft. long and 3ft. 2in. diameter, 127 tubes of 1⅞th in. diameter; the total heating surface was 709 sq. ft.; grate area, 9.7 sq. ft. The driving wheels were 6ft. 6in. diameter, and the L. and T. 3ft. 8in. The total weight of these engines was 23 tons 19 cwt., of which 9 tons 14 cwt. was on the driving axle. The wheel base was: L. to D., 6ft. 3in.; D. to T., 5ft. 9in.

J. V. Gooch’s four-coupled, or “Butterflies,” had leading wheels 3ft. 8in. diameter, and driving and trailing (coupled) 5ft. 6in. Wheel base, L. to D., 6ft. 3in.; D. to T., 7ft. 9in. The cylinders were 15in. diameter, the stroke being 24in. The boilers of this class, and also of the singles, next to be described, were of the same dimensions as those of the “250” class of tanks.

The “single” expresses were provided with 6ft. 6in. driving wheels, and cylinders 15in. diameter and a 22in. stroke; in this class also the leading and trailing wheels were 3ft. 8in. diameter. The wheel base was 14ft., the driving wheels being 6ft. 9in. from the leading and 7ft. 3in. from the trailing wheels. Ten engines of this design were constructed, some at Stratford, and others at the then recently opened Canada Works of Brassey and Co. at Birkenhead. Their official numbers were from 274 to 283.

The “Ely” (Fig. 63) represents the type of 6-wheel passenger engine in use on the Taff Vale Railway at this period. She was built in 1851 by Messrs. Kitson and Company, from Taff Vale designs. She had 13in. cylinders, with 20in. stroke, and four-wheels-coupled, of 5ft. 3in. diameter. She carried a pressure of 100lbs., she had a four-wheel tender, carrying 900 gallons of water, and as the gross weight of the tender was about 11 tons in working order, the gross weight of the engine and tender would be 33 tons. The “Ely” could not take a train of three carriages, weighing only 21 tons, up the Abercynon bank of 1 in 40 without the assistance of a “bank” engine.

In 1851 Mr. Beattie, the locomotive superintendent at Nine Elms, built for the London and South Western Railway the four-wheels-coupled engine, “Hercules,” No. 48. The frames of this engine were of the “lattice” type, examples of which can be still seen on some of the older Great Northern Railway tanks.

The diameter of wheels was: L., 3ft. 6in.; D. and T., 5ft. 6in.; tender, 3ft. 6in.; wheel base, L. to D., 7ft. 1in.; D. to T., 6ft. 6in.; T. to leading tender, 7ft. 3½in.; the tender wheel base being 10ft. 3in. equally divided.

The weight was distributed as follows:—Engine, L. axle, 8 tons 17 cwt.; D., 9 tons 17 cwt.; T., 9 tons 16 cwt.; tender, L., 4 tons 19 cwt.; M., 6 tons 19 cwt.; T., 7 tons 10 cwt. The cylinders were 15in. by 22in.; tractive force on rail, 7,500lb.; 1,800 gallons of water could be carried in the tender tank. The “Hercules” had a flush top boiler, and a raised fire-box surmounted by a large inverted, urn-shaped dome. This design of locomotive was a favourite one on the London and South Western Railway for many years, but the last engine of the kind has now been scrapped.

Having favoured the London and South Western Railway, to equalise matters, we cannot do better than give a description of a locomotive belonging to its cousin-german, the London and North Western Railway. The latter was indeed the more famous, being no other than McConnell’s notorious “No. 300,” (Fig. 64) which, being introduced with a vast amount of publicity, became a nine days’ wonder, then sank into quiescent mediocrity, and after a brief locomotive career, was seen no more—a rather different fate, be it observed, to that of the London and South Western Railway’s “Hercules.”

It has been stated that only one drawing of this engine exists. This is incorrect; the writer possesses a complete set of drawings relating to “No. 300,” together with the whole of the specifications from which the engine was constructed. To reproduce this specification in detail would give too technical a character to this narrative, and would try the patience of even the most ardent locomotive enthusiast.

The directors of the London and North Western Railway in 1851 expressed their determination to run their express trains from London to Birmingham in two hours, and gave instructions to McConnell, the locomotive superintendent at Wolverton, to design the necessary locomotives. The salient features of the design were: Inside cylinders, 18in. by 14in.; six wheels, with inside and outside frames; driving wheels, 7ft. 6in. diameter; leading, 4ft. 6in.; and trailing, 4ft. diameter.

The boiler was 11ft. 9in. long and 4ft. 3¼in. external diameter. The tubes were of brass, 303 in number, only 7ft. in length, and 1¾in. outside diameter. The crank axle bearings were—outside, 7in. deep and 10in. in length, the inside ones being 7in. and 4¼in. respectively. The leading and training axles were hollow, the metal being 1½in. thick, and the hollow centre 4½in. diameter, thus making the total diameter of the straight axles 7½in. The slide-valves had an outside lap of 1¼in. The principal innovations were: Coleman’s patent india-rubber springs, fitted below the driving axle and above the leading and trailing axles, and also to the buffers. McDonnell’s patent dished wrought-iron pistons, forged in one piece with the piston-rod, and encased with continuous undulating flat metal packing. The steam-pipe was of flat section, and passed through a superheating chest in the smoke-box; the steam was thus dried during its journey from the dome to the cylinders. The great feature of the design was the arrangement of the fire-box, with a mid-feather, a combustion chamber, hollow stays for a free supply of air to the fire-box, and the cutting away of the bottom of the fire-box to obtain clearance for the cranks and yet retain a low centre of gravity with large driving wheels. Assertion to the contrary notwithstanding, it should be observed that so much did McConnell insist upon a low centre of gravity that he specially mentioned it in his patent specification of February 28th, 1852.

A more particular description of the fire-box, etc., is requisite. It extended into the cylindrical portion of the boiler a distance of 4ft. 9in., so that the boiler tubes were only 7ft. long. The whole length of the fire-box was 10ft. 6in.; depth at front-plate 6ft. 5in., at door-plate 6ft. 10in.; length on fire-bars 5ft. 10¼in., thus leaving 4ft. 7¾in. for the portion over the axle and the combustion chamber. At its narrow part (directly at the top of the recess above the driving axle) the fire-box was only 2ft. 3in. in height; height at tube-plate 3ft. (beyond the cut away portion); width at tube-plate 3ft. 9in. It will be noticed that Webb’s “Greater Britain” class of locomotives is designed with the long fire-box and combustion chamber; but as Mr. Webb, unlike McConnell, does not object to the high pitched boiler, the former does not recess the boiler barrel for the purpose of obtaining a low centre. Webb also divides his tubes into two sets by having the combustion chamber between them. McConnell’s combustion chamber was a continuation of the fire-box. We must now describe the general appearance of this engine.

The cylinders were inclined upwards from the front, and the valve chests were above them, below the smoke-box. Two Salter safety valves were provided, encased within a sheet-brass covering of Stirling’s Great Northern pattern. The steam pressure was 150lbs. The dome was also of brass, with a hemispherical top surmounting the cylindrical lower part. The steam regulator was at the mouth of the steam-pipe, which was placed at the top of the dome (inside, of course).

The heating surface was: Tubes, 980 sq. ft.; fire-box, 260 sq. ft. Wheel base, 16ft. 10in. Sufficient steam could be raised in 45 minutes after lighting the fire to move the engine. Two of these engines were built about the same time—one (No. 300) by Fairbairn and Co., Manchester, the other by E. B. Wilson and Co., Leeds. The orders were given early in July, 1852, and the engines delivered the second week in November, Wilson and Co. having occupied but eight weeks in the construction of the one given to them.

Both engines were delivered at Wolverton on the same day, and on Thursday, November 11th, 1852, Wilson’s engine was tried for the first time, when on her first journey to Euston she attained a speed of 60 miles an hour.

It was soon found that “No. 300” and her sister engine were unable to cover the 111 miles—Euston to Birmingham—in two hours, as was confidently predicted, and the failure to do so was—perhaps justly—attributed to the inferior condition of the permanent-way. On March 8th, 1853, “No. 300” hauled a train of 34 carriages, weighing 170 tons, from Birmingham to London in three hours eight minutes, including five stoppages. A similar train drawn by the “Heron” and “Prince of Wales” took ten minutes longer to perform the same journey. These two engines had cylinders 15in. by 20in., and 6ft. driving wheels. The results of this trial are thus tabulated:—

Upon the result of this run it was claimed that McConnell’s patent engines were considerably superior to two of the ordinary London and North Western Railway locomotives, and one of Stephenson’s “long boiler” abortions was altered by McConnell, being fitted up with his patent combustion chamber, short tubes, and the other innovations, as mentioned in our description of “No. 300.”

The “long boiler” originally had 1,013 sq. ft. of tube-heating surface; when altered, the length of the tubes was reduced to 4¾ft., and some additional ones were fixed diagonally across the combustion chamber. By this alteration the tube-heating surface was reduced to 547 sq. ft., and the engine is stated to have drawn 170 tons at 60 miles an hour, and to have attained a speed of 70 miles an hour with light trains. From the working of this locomotive the following table (by which a reduction of 23 per cent. in the amount of fuel consumed was claimed for the altered engine) was prepared:—

But D. K. Clark’s paper on “Locomotive Boilers,” read before the Institution of Civil Engineers, soon placed a very different complexion upon the result of the trials between the ordinary and patent engines, resulting in the “air-tubes” to the combustion chamber being speedily abandoned. The attention of the directors of the London and North Western Railway was called to the failure of these engines, with the result that they ordered Messrs. Marshall and Wood to report on the two classes of engines—viz., the ordinary London and North Western type and McConnell’s patent locomotives. This report was ready in August, 1853, but for some reason its publication was suppressed at the time, but the directors countermanded the construction of other engines already ordered on McDonnell’s patent principle.

In the summer of 1854 Marshall and Wood conducted another set of experiments for the directors of the London and North Western Railway, with the object of determining the relative value of coke and coal as fuel for the locomotives.

The engines chosen were McConnell’s patent “No. 303” and the “Bloomer,” No. 293. Double trips were run between Rugby and London daily for six consecutive days, coal being burnt on three days and coke on the three alternate days. The trains chosen were the 12.55 p.m. up and 5.45 p.m. down.

It was found that 1lb. of coal evaporated 5.83lb. of water, and 1lb. of coke 8.65lb. of water; but the monetary saving was 6s. 9d. per ton in favour of coal.

McConnell’s patent engines were again condemned. Marshall and Wood’s report concluded as follows: “Although we consider the experiments we made with No. 303 engine satisfactory in point of smoke burning, we cannot resist the belief that the consumption of coal is in excess of what it ought to be, and that there is room for considerable improvement in this respect, by means which shall tend to utilise the heat which is at present wasted.”

The whole report is of great interest to the technical reader; it is, however, too long to reproduce in extenso.

It is abundantly evident that there is no great pecuniary gain from locomotive designing, or we should be treated to great law-suits regarding the validity of the patents, such as have recently been the case with pneumatic tyres and incandescent gas-burners. We have already, upon more occasions than one, pointed out that certain patented locomotive designs had previously been anticipated, although the later patentees were probably unaware of the fact. We find this to have been the case with McConnell’s “recessed” boiler locomotives just described, for on December 2nd, 1846, W. Stubbs and J. J. Grylls, of Llanelly, enrolled a design of locomotive. The specification in question not only mentioned the recessing of the boiler for the purpose of allowing the use of a large driving wheel and yet retaining a low centre of gravity, but it even anticipated McConnell’s combustion chamber between the fire-box and tubes. An adaptation of Bodmer’s double piston motion was also specified by Stubbs and Grylls. The two cylinders were placed below the boiler, four wheels being connected by means of side-rods with the cross-heads of the two cylinders in such a manner that from each cylinder two wheels were driven, by means of a cross-head, and each cross-head, by means of two connecting-rods, rotating the wheels. Another claim under this patent related to driving a locomotive by eccentrics fitted with antifriction rollers as a substitute for the ordinary cranks.

Although in the “Evolution of the Steam Locomotive” it is only intended to describe locomotives for British railways, it may not be out of place to mention an engine for a foreign railway, for two reasons—first, because it was built by an English firm in England, and, secondly, because it was tried on an English railway before exportation. The “Ysabel” was constructed in 1853 by Dodds and Sons, of Rotherham, for the “Railway of Isabella II. from Santander to Abar del Rey,” and was tried on the Lickey incline of 1 in 37 for two miles, under the direction of Mr. Stalvies, the locomotive superintendent at Broomsgrove. The “Ysabel” had four-coupled wheels 4ft. 6in. diameter; cylinders, 14¼in. by 20in. stroke; 137 tubes, 1⅞in. diameter, and 11ft. 3in. in length, and was fitted with Dodds’ patent wedge expansive motion, which required only two eccentrics. For the purpose of easy transportation, the “Ysabel” was so constructed that when disconnected no single portion weighed more than six tons; in addition to the fittings necessary to secure the boiler, the only connections between it and the frames, machinery, etc., were the steam-pipe and the two feed-pump connections. When tried upon the Lickey bank this locomotive hauled six trucks weighing 45 tons 12¾ cwt. up the two miles one furlong in 12 minutes 12 seconds, and with a train weighing 29 tons 4¼ cwt. the incline was negotiated in seven minutes five seconds.

The compound locomotive is not quite so modern an invention as is popularly supposed, for, putting aside the suggestion emanating in 1850 from John Nicholson, an Eastern Counties Railway engine-driver, whose plan of continuous expansion is generally accepted as the foundation of the compound system, we find that in 1853 a Mr. Edwards, of Birmingham, patented a “duplex” or in other words a compound engine, the steam, after working in a high-pressure cylinder, being used over again in a low-pressure one. The cylinders were so placed that the dead centre in one occurred when the other piston was at its maximum power.

In 1853 Beattie constructed for the London and South Western Railway at Nine Elms Works, the “Duke,” No. 123, a six-wheel “single” express engine; driving wheels, 6ft. 6in. diameter; L. and T. 3ft. 6in. diameter; cylinders, 16in. by 21in. stroke. The weight was arranged in an extraordinary manner, 10 tons 9 cwt. being on the leading axle, only 9 tons 9 cwt. on the driving axle, and 5 tons 11 cwt. on the trailing axle. The wheel base was, L. to D., 6ft. 8½in.; D. to T., 7ft. 6in. The “Duke” had a raised fire-box, surmounted by a large dome similar to that of the “Hercules,” whilst another dome was located on the centre of the boiler barrel. The shape of this centre dome resembled a soup-tureen turned upside down.

At this point we take the opportunity to briefly describe a railway locomotive which, although not propelled by steam, deserves to be mentioned as an initial attempt at railway haulage by means of compressed air.

The engine in question was constructed by Arthur Pasey, and was tried on the Eastern Counties Railway in July, 1852. This machine was, in point of size and power, nothing more than a model, the dimensions being: Cylinders, 2½in. diameter, 9in. stroke; driving wheels, 4ft. diameter; weight, 1½ tons; air capacity of reservoirs, 39 cubic ft.

By reference to the illustration (Fig. 65) it will be seen that this curious little locomotive had the six wheels of 4ft. diameter within the frames, and the horizontal cylinders outside the frames, and actuating the centre pair of wheels. Above the frames was placed a cylindrical air reservoir, with egg shaped ends. This extended from the buffer beam at one end of the vehicle to the leading axle, a distance of about 12ft. The remainder of the space, about 4ft., was occupied by the pressure-reducing and other apparatus, and afforded a place of vantage for those in charge of the machine. The reservoir was constructed to withstand a pressure of 200lb., but the engine was only pressed to 165lb., and this at the time of the trial at Stratford was reduced to 20lb. working pressure. With a load of eight people, the engine ran the four miles, Stratford to Lea Bridge and back, in 30 minutes. The incident of the trial so aroused the curiosity of the men engaged at the Stratford Works, that they all left their employment for the purpose of witnessing the trial of so great an innovation as Pasey’s compressed air locomotive. For this reason no further trials could be held at Stratford, but on July 2nd a second trip was made at Cambridge, and on this occasion, with six passengers, the following results were recorded: Starting from the 60th mile-post near the Waterbeach Junction, with a working pressure of 15lb. per sq. in., the first mile was covered in five minutes. By increasing the pressure on the pistons, the second mile was covered in four minutes; the pressure was then reduced to 18.85lb., and 3½ additional miles were covered in ten minutes. The designer of this little machine gives eight reasons by which he apparently succeeds—at all events to his own satisfaction—in proving the great superiority of compressed air traction over that of steam. Unfortunately for Mr. Pasey’s theory, steam is still triumphant, and compressed air dead—or nearly so—for tractive purposes.

The opening of the Great Northern Railway next claims our attention. The first locomotives were supplied by contract, an order for 50 passenger engines having been given to Sharp Bros. and Co. These were six-wheel single engines (Fig. 66), the driving wheels being 5ft. 6in. diameter. The cylinders were 15in. by 20in. stroke. Weight of engine, loaded, 18 tons 8½ cwt. These engines were called “Little Sharps,” and (Fig. 66) is an illustration of one of them.

We will now describe the famous “No. 215” (Fig. 67) of the Great Northern Railway, designed towards the end of 1852 by Mr. Archibald Sturrock, constructed by Hawthorn and Co., Newcastle, and delivered to the Great Northern Railway on August 6th, 1853.

Fortunately, Mr. Sturrock has supplied the writer with complete and authentic details, together with a drawing, of this engine, so that readers may rely upon the information being strictly accurate, although it should be noted that it does not correspond in several particulars with other statements concerning “No. 215” that have been published.

It is a matter of railway history that in 1852 the “Gladstone” award settled the great rivalry existing at that period between the London and North Western and Great Northern Railways. The competition had been carried on in a manner still in favour in American railroad warfare—viz., the cutting of rates and fares; but Mr. Gladstone having decided this point, the Great Northern Railway introduced the method of rivalry now universally recognised as English railway competition—that is, trial of speed. Mr. Sturrock, with the experience gained under the daring broad-gauge leaders, was, of course, conversant with what a locomotive could do, and his published reasons for the construction of “No. 215” are as follow:—

“This engine was constructed to prove to the directors of the Great Northern Railway that it was quite practicable to reach Edinburgh from King’s Cross in eight hours, by only stopping at Grantham, York, Newcastle, and Berwick. This service was not carried out, because there was no demand by travellers for, nor competition amongst, the railways to give the public such accommodation.”

Although delayed for 35 years, the demand for such a service arose in 1888, and Mr. Sturrock then had the satisfaction of seeing runs such as he had built “No. 215” to perform become daily accomplished facts. It should be noted that when “No. 215” was originally built, she was fitted with a leading bogie, such an arrangement being a principal feature of Mr. Sturrock’s original design for the engine. The bogie and trailing wheels were 4ft. 3in. diameter, the driving wheels being 7ft. 6in. diameter; the cylinders were inside, and had a diameter of 17½in., with a stroke of 24in. The heating surface was large, this being another of the strong points in Mr. Sturrock’s design. Tubes, 1,564 sq. ft.; fire-box, 155.2 sq. ft.; total heating surface, 1,718.2 sq. ft. The weight was, empty, 32 tons 11 cwt. 2 qr.; in working order, 37 tons 9 cwt. 2 qr. Wheel base, 21ft. 8½in. Water capacity of tender, 2,505 gallons. The frames and axle bearings were outside; the latter were curved above the driving axle, as in the broad-gauge “Lord of the Isles” type.

The boiler and raised fire-box were also after the same pattern. The engine had no dome, but an encased safety valve on the fire-box—a further evidence of attention to the Swindon practice. Compensation beams connected the two pairs of bogie wheels, and the underhung springs of the driving wheels were also connected with the trailing axle springs by means of compensation levers. “No. 215” frequently ran at 75 miles an hour. She appears to have been broken up about 29 years back, for in 1870 Mr. Stirling built an engine, “No. 92,” in which he used the 7ft. 6in. driving wheels of Mr. Sturrock’s famous “215.” Engine No. 92, is still at work, so that the driving wheels must be 45 years old. A comparison of Mr. Sturrock’s “215” with McConnell’s “300” will show the immense superiority of the former, especially with regard to the amount of heating surface, the pitch of the boiler, and the bogie in place of the rigid wheel base.

In the last chapter, Mr. Pearson’s initial patent for a locomotive was described, and a description of his famous double-bogie tank engines, with 9ft. “single” driving wheels, is given below. The design (Fig. 68), which was brought out in 1853, was a modification of the patent specification already alluded to. The engines were constructed by Rothwell and Co., Union Foundry, Bolton-le-Moors, and were famous for the low average cost for repairs and fuel consumption per mile run; indeed, a feature of most of the broad-gauge locomotives was the low average cost of maintenance and working. The ends of the frames were supported on a four-wheel bogie, the wheels of which were 4ft. in diameter, and the driving wheels 9ft. diameter; these latter had no flanges. The cylinders (the ends of which projected beyond the front of the smoke-box) were 16½in. diameter and 24in. stroke; the driving axle was above the frame. The boiler was 10ft. 9in. long and 4ft. ½in. diameter; it contained 180 brass tubes of one and thirteen-sixteenths inch external diameter. The steam pressure was 130lb. No dome was provided, and the Salter safety valves were located on the top of the fire-box and enclosed by a brass casing. The weight of the engine, in working order, was 42 tons. The water was stored in three tanks, one beneath the boiler, another below the fire-box, and the usual well tank, behind the foot-plate. The two suspended tanks were connected by means of a stuffing-box jointed pipe, which was continued to the bottom of the wheel tank, so that the water in the three tanks was thus able to pass from one tank to any other one. The feed pumps were worked from the piston-rod cross-head, and the feed-pipes passed along behind the splashers to the boiler. To steady the suspended tanks, link-rods were passed between the two. There were also “bogie safety links” connecting the bogie frames with the main frame at each end, and similar links connected the suspended tanks with the other ends of the bogie frames.

These links were each fitted with india-rubber disc buffers, to allow of the necessary elastic working. The parts were thus so strongly linked together, that should a bogie centre-pin break, or should the bogie movement fail in any way, the wheels would still remain in their right position. The whole of the springs were of the india-rubber disc kind. Those of the driving axle presented some remarkable peculiarities.

They were double, an elastic connection being formed between the boiler and the axle-boxes by large plate brackets projecting from the boiler barrel, and carrying centre studs for a short double-armed lever; each end of this lever had a separate spring-box attached to it by a long link.

The inner spring-box worked down behind the disc plate of the driving wheel splashers, whilst the outer one worked parallel to it, outside the driving wheel.

The springs for the other wheels were all beneath their axles, and were very compact and neat in appearance. The brake action was confined to the after bogie, all four wheels being used for the frictional effect, the sliding bars carrying the brake blocks being actuated in reverse directions by a screw spindle, which carried a winch to be worked by the driver.

The regulator valve was a slide, worked in a simple and certainly a convenient manner by a short lever, set on a pillar stud on the front of the fire-box, and passing through a slot in the end of the slide spindle. This was a far more effective plan of working the valve than the ordinary rotatory handle.

These engines were remarkable for their steady running at high speeds, 80 miles an hour and over being a daily performance of the engines on certain portions of the main line between Exeter and Bristol.

One reason for the freedom from excessive oscillation for which these engines were famous was attributable to the 9ft. driving wheels, and the slow piston velocity arising therefrom; thus with 6ft. wheels at a speed of 60 miles an hour, the pistons have to make no less than 280 double strokes per minute without making allowance for “slip.” With the 9ft. driving wheels the double piston strokes per minute at 60 miles an hour fall to 186, and consequently with so considerable a reduction in the movements of the reciprocating and rotating machinery of the locomotive, it is only reasonable to expect and obtain a much more steady movement of the machine.

In the matter of coal consumption the engines were no less successful. Writing in August, 1856, Mr. Pearson reported: “Engine No. 40 has run 81,790 miles since her delivery in October, 1853, and has consumed 794 tons 17 cwt. 2 qr. of coke, or 21.76lb. per mile; the repairs as yet have been very trifling, consisting chiefly of re-turning the tyres. This engine has been working passenger trains on the main line almost the whole of the time since she was delivered. Our mileage is rather heavy, each engine averaging 750 miles per week.”

After 1876, when the Bristol and Exeter Railway was amalgamated with the Great Western Railway and the former company’s locomotive stock became the property of the latter, 4 of the 8 original 9ft. tank engines then in existence were rebuilt, and their character and design entirely remodelled. The diameter of the driving wheels was reduced to 8ft., and tyres fitted to them, a pair of trailing wheels were provided in place of the rear bogie, and a separate tender was added, the tanks being done away with. The B. and E.R. numbers of these engines were 39 to 46. The G.W.R. numbered the four taken over 2001 to 2004. The latter was hauling the “Flying Dutchman” when the Long Ashton accident happened on July 27th, 1876. It was in consequence of this disaster that the engines were rebuilt with 8ft. wheels. In concluding this sketch of Pearson’s famous broad-gauge double tanks, we may state that until recent years, when phenomenally high locomotive speeds have been recorded, these engines held the “blue ribbon” in that respect with an authenticated speed of 81 miles an hour. Figures 69 and 70 represent them as rebuilt.