Chapter I: 1 (2)

The more modern and simple method of working out the same idea is to connect the main zigzag lines by curves or _spirals_, thus rendering the route continuous and unbroken. By this arrangement the heavy work and delay in starting or stopping the train at the apices, A, B, and C, as shown on Fig. 25, is avoided, and the train can proceed continuously on its circuitous journey. Fig. 26 shows an instance of the zigzags and spirals, as carried out on an important railway abroad. To have made a direct line from D to E, the most difficult part of the route, would have involved a gradient of 1 in 11; but by constructing the spiral course, as shown, the length was more than trebled, and the gradient reduced to 1 in 35.

Fig. 27 is another example of spiral zigzags in which advantage was taken to cut a short tunnel through a high narrow neck of rock at G, and then by skirting round the hill the line was taken over the top of the tunnel and along the side of the mountain to the summit tunnel at H. By this means the line from F to H was laid out to an average gradient of 1 in 42.

Fig. 28 shows the Cumbres inclines on the Mexican Railway. The route had to be located through one of the rugged passes of the great Chain of the Andes, whose mountain-sides rise most abruptly from the lower plains, to the great upper-land plateau, some eight thousand feet above sea-level. The ground to be traversed was so steep and difficult that, even with the best available detours and greatest length that could be obtained, the result was an average continuous gradient of 1 in 25 for 12 miles.

Fig. 29 is a plan of part of the St. Gothard Railway, showing the principal tunnel 9¼ miles long, and some of the adjoining spiral tunnels. The long tunnel through the great Alpine barrier was the only means of forming a railway connection between the two points at Airolo and Goeschenen. Constructed in a straight line, with easy gradients, 37 falling towards the entrances, efficiency of drainage has been secured, and excessive strain on motive-power avoided. The approaching valleys on each side were in some places too irregular and broken to admit of zigzag loops, and the spiral tunnels were adopted instead. The enlarged plan of two of the spiral tunnels will explain the method of working. An ascending train enters the first tunnel at A, and after passing round almost an entire circle, on a rising gradient, emerges at a much higher level at the point B. Proceeding onward, the train enters the second tunnel at C, and after passing round a similar circle, on a rising gradient, comes out at a still higher point, D, and continues its course up the valley.

The last five sketches illustrate some of the methods which have been adopted when constructing railways through some of the most difficult mountain ranges. They show what has been done, and may serve as guides in working out the location of a line in some hitherto unexplored region.

Gauge.--The gauge of a railway, or its width from inside to inside of rails, affects both its cost and efficiency. If the gauge be exceptionally wide, then the expenditure on works and rolling-stock will be proportionately heavy; and although theoretically the extra wide gauge may possess greater capabilities for accommodation and high-speed travelling, we may find in practice that the necessary requirements may be provided on a much more moderate gauge. On the other hand, if the gauge be exceptionally narrow, there will be diminished convenience both for passengers and merchandise, and a corresponding limit to the speed in transit.

In isolated districts, where passenger traffic is of secondary importance, and where the principal merchandise will be heavy without being bulky, such as mineral ores, slates, etc., a comparative narrow gauge may possibly suit the purpose. For main trunk lines, however, where a large, heavy, and fast passenger traffic will have to be worked, and where goods of all kinds, many of them bulky without being heavy, will have to be carried, an ample gauge must be selected to ensure convenience and safety. A liberal gauge permits the use of commodious rolling-stock without any great amount of lateral overhanging weight outside the wheels; whereas with a narrow gauge there is the tendency--if not the necessity--to use vehicles which have too great a lateral overhang for proper stability, except at very 38 moderate speeds.

The following list shows the gauges adopted in various countries:--

ft. ins.
England, Scotland,
and Wales 4 8½
Ireland 5 3
United States 4 8½, with some lines 5 ft., 5 ft. 6 ins., and 6 ft.
Canada 4 8½ and 5 ft. 6 ins.
France 4 8½
Belgium 4 8½
Holland 4 8½
Germany 4 8½
Austria 4 8½
Switzerland 4 8½
Italy 4 8½
Turkey 4 8½
Hungary 4 8½
Denmark 4 8½
Norway 4 8½ and 3 ft. 6 ins.
Sweden 4 8½
Mexico 4 8½ and 3 ft.
Egypt 4 8½ and 3 ft. 6 ins.
Peru 4 8½
Nova Scotia 4 8½ and 5 ft. 6 ins.
New South Wales 4 8½
Brazil 4 8½, 5 ft. 3 ins., and 5 ft. 6 ins.
Uruguay Republic 4 8½
Russia 5 0
South Australia 5 3
New Zealand 3 6
British India 5 6 and 1 metre.
Ceylon 5 6
Spain 5 6
Portugal 5 6
Chili 5 6
Argentine Republic 5 6
Cape Colonies 3 6
Japan 3 6

After many years’ experience of actual working, the broad, 7 feet, gauge of the Great Western Railway has been abandoned for the 4 feet 8½ inch gauge. Doubtless this decision was the result of most careful deliberation, and was made upon convincing proof that the 4 feet 8½ inch gauge could fulfil all the advantages claimed for the wider gauge, whilst at the same time it possessed the merit of less cost of construction and working, and greater facilities for the exchange of traffic with other lines having the standard gauge. The facility of exchange, or through working of rolling-stock, is a leading element of successful railway working, and it is difficult to estimate what would be the amount of loss and delay if we had any great extent of break of gauge on the main trunk lines of our own country.

Although some countries have selected gauges of 5 feet and 5 feet 39 6 inches, it is interesting to note that the largest number have adopted the English standard gauge of 4 feet 8½ inches, and that the miles of line laid to this gauge far outnumber all the others. The fact that our own home lines, the principal Continental lines, and nearly all that vast network of railways in the United States of America, have been laid to the 4 feet 8½ inch gauge, testifies to the general opinion of its utility and efficiency; and we know that included in that list are the railways which carry the largest, heaviest, and fastest train service in the world.

It would be interesting to trace back, and, if possible, ascertain from whence the exact gauge of 4 feet 8½ inches was derived. No doubt, in the early days of the pioneer iron highways in England, the railways were made the same gauge as the tramroads which they superseded. But why was 4 feet 8½ inches the gauge of the tramroads? We may reasonably infer that the first four-wheeled waggons used on the early tramroads were in reality the same waggons which had been previously used on the common roads for the conveyance of coal and minerals to the ports for shipment, and that the waggons were merely transferred from the roughly paved or macadamised roads to the tramroads. Flanged wheels were then unknown, and the introduction of the tram-plates was at first simply designed to lessen the resistance to haulage. The gauge, or width between the wheels, of these waggons may have been the outcome of long experience as to the most suitable width for convenience of load, stability during transit, or for space occupied on the highway. The width may have been handed down from generation to generation, going back to the time when wheeled vehicles were first built in the country. Perhaps in the beginning the first vehicles may have been imported from Italy, or Greece--countries which in the earlier ages were the most advanced in matters of luxury and convenience.

When in Pompeii, a few years ago, the writer measured the spaces between a large number of the _wheel-ruts_ which are worn deep into the paving-stones in many of the principal streets of that wonderful unearthed city. These paving-stones, very irregular in shape, and many of them 2 feet 6 inches long by 1 foot 6 inches wide, are carefully fitted together, and form a compact massive pavement from curbstone to curbstone. The wheel-tracks, which are in many places worn into the stones to the depth of an inch or an inch and a 40 half, are always distinct, and there is no difficulty in defining the corresponding track.

The result of a large number of measurements gave an average width of about 4 feet 11 inches from centre to centre of the wheel-tracks, a curious coincidence with the gauge of our own road vehicles at the beginning of the railway era. Whether our selection of the railway gauge of 4 feet 8½ inches has been the result of study, imitation, or caprice, we certainly have the silent testimony of these old deep-worn stones to prove that two thousand years ago the chariots of Pompeii were of very similar gauge to our own of modern times.

Narrow-gauge railways, of gauges varying from 1 foot 10½ inches on the Festiniog Railway, to 3 feet, 3 feet 3 inches (metre), and 3 feet 6 inches, have been made in several places both at home and abroad. Generally speaking, they have been constructed as subsidiary or auxiliary lines in thinly populated districts, with a view to afford some railway accommodation where it was considered that lines of the standard gauge would not pay. In some instances abroad long lines of narrow gauge--3 feet and 3 feet 6 inches--have been constructed as main trunk lines in newly opened out districts. Some of these have since been altered to a wider gauge as the traffic developed, and experience proved that the narrow width of the vehicles was unsuitable for quick transit, or convenience in the accommodation of passengers and goods.

The object in making a line to a narrow gauge is doubtless to save cost in the original construction; but when a scheme for an altered gauge is put forward, it will be well to consider what amount of advantage or saving would be effected by deviating from the standard gauge.

If there be almost a certainty that such proposed line will always remain isolated from all other existing railways of the standard gauge, then perhaps the selection of gauge may be one of minor importance, and there remains but the question whether the description of traffic, and the weights to be carried, can be worked to any greater advantage, or more economically, by deviating from the standard gauge.

If, however, there be a fair probability that such proposed line may at some future time become part of an already established railway system, it would appear to be more prudent to make the line to the standard gauge, and effect economies by introducing steeper gradients, 41 sharper curves, and lighter permanent way, and keep down working expenses by using lighter locomotives, worked at slower speeds.

High speeds are not expected on narrow gauge railways, and no complaints are made about passenger trains whose highest running speed does not exceed 20 miles per hour. By conceding the same indulgence to light railways made to the standard gauge, great economies might be introduced both in their construction and working. The similarity of gauge would admit the transit of the carriages and waggons of other standard gauge lines, and so avoid all cost and delay in transshipment. The heavy engines could be kept for the main-line working, and light engines for slow speeds would serve for the light standard-gauge lines. As traffic developed, and the train service required heavier and faster trains, the light rails could be removed, and replaced by those of heavier section to correspond to the main line. The similarity of gauge would permit uninterrupted transit of all vehicles to a common centre for repairs, whereas the narrow gauge carriages and waggons, being limited to running only on their own district, must have separate workshops for their repair.

When considering the cost of construction and working of a narrow-gauge railway as compared with one of the standard gauge, there are certain items which are common to both, and in which the narrow gauge could not be expected to obtain any advantage over the standard gauge.

There would not be any saving in getting up the scheme in the first instance;

Nor in the Parliamentary expenses;
Nor in the engineering or carrying out of the works;
Nor in the station accommodation, waiting-rooms, and offices;
Nor in the signals and interlocking arrangements;
Nor in the telegraph;
Nor in the working staff and train men;

Nor in the maintenance of the permanent way, as the same number of men would be required for the inspection and packing of the road, perhaps more.

Little or no saving could be expected in the bridges under the railway, as these must be made to the prescribed widths and heights, irrespective of the gauge of the railways.

Little, if any, saving could be made in river or stream bridges, as the 42 same amount of waterway would have to be provided in each case.

The same remark applies to culverts and drains.

There would, on the other hand, be a small saving in the quantity of land to be acquired to the extent of a narrow strip or zone, represented by the difference in width between the narrow and standard gauges.

There would also be the same small proportionate saving in the embankments and cuttings to the extent of the difference in gauge.

Also a saving in the overline bridges and road approaches in consequence of less width and height of the opening through those bridges.

And a saving in the rails, sleepers, and ballast of the permanent way, to the extent consistent with efficiency. That some saving may be effected in these is undoubted, but it is necessary to exercise caution, and not rush to the opposite extreme by making the parts too light. A rail should be made not only strong enough to carry well the engines that have to pass over it, but it should also be heavy enough to stand the wear of several years. Narrow-gauge engines must be heavy in conformity with the loads they have to haul. The same amount of power must be exerted to haul a hundred tons on a given gradient, whether the gauge be narrow or broad. In some cases of narrow-gauge railways the original rails, which weighed only 45 lbs. per yard, have since been replaced with others weighing 60 and 65 lbs. per yard. The light 45 lb. rails were evidently not found to be sufficiently heavy to keep the road to proper line and level. The result of our everyday practice seems to prove that there is not only an advantage, but an economy, in adopting rails of a heavy section, and experience would therefore indicate that even for a narrow-gauge railway it may not be expedient to adopt rails weighing less than 65 lbs. per yard.

Gradients.--There are very few localities where the rails on any line of railway can be laid perfectly level or horizontal for more than comparatively short distances. By far the greater portion have to be laid on inclined planes of varying rates of inclination to suit the general formation of the district traversed, and the circumstances of the line to be constructed.

The degree, or rate of inclination, of these inclined planes, or gradients, may be expressed in various ways. A very general method is 43 to state the number of feet, metres, etc., which can be measured along the gradient before an increased rise or fall of one foot or metre, etc., is obtained. Thus a gradient of 1 in 200 signifies a rise or fall of 1 foot in 200 feet, or 1 metre in 200 metres.

Sometimes the rate of inclination is expressed by stating the number of feet of rise or fall in a mile. In this way a gradient would be described as falling at the rate of 30 feet in a mile, rising at the rate of 20 feet in a mile, etc. Twenty feet to a mile is equal to 1 in 264.

Another method is to give the percentage of rise or fall. In this way the inclination would be expressed as a 1 per cent. gradient, 2 per cent. gradient, ½ per cent. gradient, etc., which for comparison would signify 1 in 100, 1 in 50, and 1 in 200 respectively.

The gradients of a railway most materially influence its facility and cost of working, and every effort should be used to make them as easy as possible consistent with the prospect of the line.

Steep gradients signify heavy locomotives, increased cost of motive-power, reduced speed, and light loads.

The following tabulated memoranda show the approximate loads, exclusive of engine and tender, which can be hauled on the level and on certain inclines at various speeds by engines of the quoted capacities and steam admissions. A medium-sized, ordinary type of passenger and goods engine has been selected for each of the examples. The working of the passenger engine and train is assumed to be under favourable circumstances, with fine weather, fairly straight line, first-class permanent way, modern rolling-stock with oil axle-boxes and perfect lubrication, and all the conditions most suitable to ensure the least resistance to the moving load. For the goods engine and train a greater resistance per ton of load is assumed, as the goods trucks are never so perfect or easy in the running as the passenger carriages. A certain amount of side wind is taken into consideration, and also an allowance for moderately sharp curves, the object being to indicate what may be looked upon as fair, average, workable loads.

The loads for engines of larger or smaller dimensions, or higher or lower pressures, may be obtained by working out the proportion between 44 the tractive force put down in any of the columns of the tabulated memoranda and the ascertained tractive force of any other engine under the same conditions of cut-off and speed.

-----------------------+-------------------------+-------------------------
| PASSENGER ENGINE. | GOODS ENGINE.
| |
|Six wheels, driving |Six wheels, all coupled,
| and trailing wheels | 4 ft. 6 ins. diameter.
| coupled, 6 ft. 6 ins. | Cylinders,
| diameter. Cylinders, | 17 ft. × 24 ft.
| 17 ft. × 24 ft. | Locked-down pressure on
| Locked-down pressure on | safety-valves, 140 lbs.
| safety-valves, 140 lbs. | per square inch. Assumed
| per square inch. Assumed| pressure at cylinders,
| pressure at cylinders, | 120 lbs. per square inch.
| 120 lbs. per square |
| inch. |
| |
|Weight of engine 39 tons.|Weight of engine 34 tons.
| ” tender 24 ” | ” tender 24 ”
| -- | --
| 63 ” | 58 ”
-----------------------+-----+-----+------+------+-----+-----+------+------
Assumed cut-off | ¼ | ⅓ | ½ | ¾ | ¼ | ⅓ | ½ | ¾
” mean effective | | | | | | | |
pressure, lbs.| 45 | 56 | 76 | 100 | 45 | 56 | 76 | 100
” tractive force,| | | | | | | |
lbs. | 4000| 4979| 6758 | 8892 | 5780| 7192| 9760 | 12844
Speed in miles per hour| 60 | 40 | 30 | 15 | 40 | 30 | 20 | 15
| | | | | | | |
|Tons.|Tons.|Tons. |Tons. |Tons.|Tons.|Tons. |Tons.
| | | | | | | |
Level | 97 | 230 | 447 | 892 | 213 | 358 | 623 | 907
1 in 1000 | 84 | 196 | 373 | 707 | 187 | 310 | 532 | 768
” 800 | 81 | 188 | 358 | 671 | 181 | 299 | 512 | 739
” 600 | 76 | 177 | 335 | 618 | 172 | 285 | 482 | 695
” 400 | 68 | 157 | 296 | 533 | 157 | 257 | 432 | 621
” 300 | 60 | 141 | 263 | 467 | 143 | 233 | 390 | 560
” 250 | 55 | 129 | 241 | 424 | 133 | 216 | 361 | 519
” 200 | 47 | 114 | 213 | 372 | 120 | 195 | 324 | 467
” 150 | 37 | 93 | 177 | 304 | 101 | 165 | 276 | 397
” 100 | 21 | 63 | 126 | 217 | 74 | 123 | 208 | 302
” 90 | -- | 56 | 114 | 197 | -- | 113 | 191 | 279
” 80 | -- | 48 | 101 | 175 | -- | 101 | 172 | 253
” 75 | -- | 43 | 94 | 164 | -- | 95 | 163 | 240
” 70 | -- | 39 | 86 | 152 | -- | 88 | 153 | 226
” 60 | -- | 28 | 70 | 128 | -- | 74 | 131 | 196
” 50 | -- | -- | 53 | 101 | -- | -- | 107 | 163
” 40 | -- | -- | -- | 73 | -- | -- | -- | 127
” 25 | -- | -- | -- | 27 | -- | -- | -- | 67
-----------------------+-----+-----+------+------+-----+-----+------+------

NOTE.--The column loads in tons are exclusive of the weight of
engine and tender.

From the above memoranda it will be seen how greatly the gradients 45 affect the loads. For an important main trunk line, with a heavy and frequent train-service of passengers and goods, the introduction of steep gradients would not only reduce the speed of the train-working, but would probably involve the necessity of assistant engines over those parts of the line; and it may be prudent, where possible, to incur heavier earthworks, or considerable detours, or tunnels, to obtain more favourable gradients. For such a line the additional cost, and the extra distance caused by a detour of a mile or more, will be of far less importance than the interruption in the train service arising from a serious reduction in speed or taking on assistant engines. On many railways abroad there are very interesting examples of long detours of several miles, carefully studied out to obtain greater length and easier gradients, resulting in the construction of lines over which the traffic can be worked without necessitating auxiliary engine-power. On the other hand, there are situations where steep gradients cannot be avoided, where certain altitudes must be reached, and where there is no alternative but to face the inevitable.

On secondary lines, and short branch lines, where the traffic is not expected to be heavy, and where speed is not so important, it may be policy to economize outlay and introduce steeper gradients than on the main line.

Half a mile of a rather steep gradient is not felt so much when it is situate midway between two stations, because the attained speed of the train assists the engine over the short distance to the summit; but when it occurs as a rising gradient out of a station, it forms a great check to the working, particularly in bad or wet weather, when there is the risk of the engine slipping, and the entire train sliding back into the station.

Long steep gradients not only necessitate increased motive-power for the ascending trains, but also require increased brake-power, and precautionary measures for the descending trains. Where passenger trains are fitted with continuous brakes, the risk of losing control is minimized; but with goods trains composed of waggons, having only the ordinary independent side-lever brake, it will be found absolutely necessary in many cases to have additional heavy brake-vans for descending the inclines, and these special vans, unfortunately, will form so much extra non-paying weight to be hauled up on the ascending trains. Of course, it is quite possible--and, indeed, in many places 46 it is customary--to pin down some of the side-lever brakes before commencing the descent, but once pinned down the brakes cannot be eased or taken off until the entire train is brought to a stand.

Every goods waggon should be fitted with a brake, and it would be of immense value if that brake could in all cases be applied and controlled when the train is in motion.

The American type of long goods waggon, with a four-wheel bogie-truck at each end, is fitted with a brake very similar to those adopted on the ordinary horse tram-cars. On the top of the waggon a horizontal iron hand-wheel, about 18 inches in diameter, is fixed on to a strong vertical iron rod, which works in brackets, and extends down below the underside of waggon framing. One end of a short length of chain is secured to the foot of the vertical rod, and the other end is connected by light iron rods to the series of levers which pull on the brake-blocks. By rotating the horizontal hand-wheel the chain is coiled round the lower end of the vertical rod, the brake-levers are pulled over, and brake-pressure applied to the wheels of the waggon. The brakesman is supplied with a convenient seat and footboard, and on the floor-level of the latter there is a pawl and ratchet attached to the vertical rod, which permits the brakes to be applied to the extent required. The pawl retains the brakes in position until the brakesman with his foot pushes the pawl out of the notch of the rachet and releases the brake gearing, which is at once pulled off quite clear by strong bow-strings attached to the framework of the bogies.

This type of hand-brake is, perhaps, the simplest that can be made. The brakesman has merely to put it on, the pawl and ratchet keep it on, and the bow springs take it off when no longer required. Each one of these long, loaded goods waggons becomes a very serviceable brake-van, and for ascending and descending steep inclines all that is necessary is to take on a few additional brakesmen to manage the brakes of as many suitable waggons. These incline brakesmen, after going down, can return to the summit by the next ascending train, their small weight being a mere nothing as compared with that of special or extra brake-vans.

On some European lines it is the custom to sprag some of the goods waggon wheels when going down exceptionally steep inclines, as well as 47 applying the brakes on the ordinary and extra brake-vans. The sprag is a piece of wood, circular in section, about 2 feet 6 inches long, and 5 to 6 inches thick in the middle, tapering off to about 2 inches thick at the ends. When the waggon-wheel is just beginning to move, the sprag is inserted between the spokes, and being caught against the waggon framework, the wheel is held fast, and being unable to revolve, remains fixed, and acts like a skid upon the rails. The skidding of the wheels upon the rails wears flat places on the wheel tyres, and it is needless to mention that the practice is only resorted to in very extreme cases. Although a very primitive means for checking the speed of a descending train, or for maintaining vehicles stationary on an incline, there have been many instances where lives have been saved and accidents prevented by the prompt use of a few sprags. Solid or close wheels cannot be spragged, only wheels which have spokes or openings, and for this reason alone it would be very desirable that in every passenger and goods train there should be some spoke or open wheels which could be spragged as a last resource, in the event of a sudden emergency of brakes failing or train becoming divided on an incline.

On ascending gradients there is always the risk of a coupling breaking, and the train becoming divided. If the detached portion left behind be provided with ample brake-power, hand-brakes, or otherwise, no harm may take place beyond a little delay; but if the brake-power be insufficient or defective, and if all the wheels are solid wheels incapable of admitting a few timely sprags, then the vehicles cannot be held, but must slide back, and running unchecked would soon attain such a velocity as would cause them either to leave the rails or dash into another train standing at the last station. Many lamentable accidents have taken place arising from portions of trains breaking away and running back, and the sad experience of those casualties should call forth every effort to avert a recurrence in the future. It may not always be possible to detect a hidden flaw in a coupling, or a defect in the brake-gearing until the actual failure occurs; but it is quite possible to guard against disastrous results from such failure, by providing means to hold the vehicles, and prevent them sliding back.

For some years the writer had the entire charge of an important railway abroad on which the gradients were very exceptional, and where 48 it was absolutely necessary that he should organize the most complete precautions to prevent the possibility of trains, or portions of trains, running back down inclines. Starting from sea-level, the line, which was laid to the 4 feet 8½ inch gauge, rose to a summit of over 8000 feet, and on the mountain division there were many long gradients of 1 in 40, 1 in 33, and in one place a continuous gradient of 1 in 25 for 12 miles. The specially powerful engines reserved for these heavy inclines were each supplied with an ordinary hand-brake, a steam-brake, and a Westinghouse continuous brake. The passenger carriages, which were of considerable length, and carried on a four-wheeled bogie-truck at each end, were all fitted up with the Westinghouse brake, and in addition each carriage had its own hand-wheel brake with the pawl and ratchet gearing. All the goods waggons, which were of the American type, were fitted with hand-wheel brakes similar to those on the carriages. Special gangs of trained brakesmen took charge of the trains on these inclines, a brakesman to every carriage or waggon, and were always in readiness in case of the breakage of a coupling, or the failure in the Westinghouse brake or brakes on engine. The immunity from accidents justified the combined precautions adopted, and proved the possibility of working such severe gradients with perfect safety.

The long-continued application of the brakes on heavy inclines naturally leads to the question as to the description of wheel to be adopted for the work. Not only are the wheels subjected to very severe torsional strains, but the temperature at the circumference is raised very high in consequence of the friction. Perhaps, theoretically, the safest wheel would be one made out of a solid piece of metal, similar to the chilled cast-iron wheels of the United States, or the steel disc wheels used on some lines in Europe, in either of which holes can be left for sprags. Wheels of this description can withstand very heavy wear and tear, they are not affected by increased temperature, and they certainly have the minimum of parts to work loose. Of the built-up wheels, the strong forged-iron-spoke wheel with steel tyres shows excellent results, and always gives due warning of loosening by indications at the tyre rivets. The suddenness with which the solid wooden centre wheels sometimes break up and fall to pieces does not commend them for a service where there must be a long-sustained application of the brakes. The increased temperature which expands the 49 tyre, contracts the wood, and must loosen and weaken the entire wheel.

On all steep gradients the road-bed should be of the most substantial character, and the permanent way of a strong description, and maintained in perfect order, as the engines for working the traffic must necessarily be of a heavy type. The rails will be severely tested by the pounding and slipping of the engines on the ascending journey, and by the action of the brakes on the descending journey.

In the early days of the railway system, rope-haulage was adopted on some of the main lines for working the trains on steep inclines near the principal terminal stations. A powerful stationary engine, located at the highest point, was employed to work an endless rope which passed round large drums at the top and bottom of the incline, and was supported on sheaves or pulleys fixed between the rails. The connection between the carriages and endless rope was effected by means of a short piece of rope called the _messenger_, which was coiled round the main rope in such a manner as to be readily detached when the train reached the summit. There are many persons who will remember the time when the passenger trains were hauled by an endless rope up the 1 in 66 incline from Euston to Camden Town, a distance of about a mile and a half, and up the 1 in 48 incline from Lime Street, Liverpool, to Edge Hill, a distance of about a mile and a quarter, and several others. The rapid strides made in locomotive construction, and the increased pressure used in the boilers, enabled much more powerful engines to be built, until one by one the rope-haulage machinery has disappeared from nearly all the inclines where for years it had been considered indispensable. Rope-haulage on inclines is now very rarely met with, except at collieries and ironworks, where occasionally the rope may be seen so arranged that the loaded waggons descending pull up the empty waggons on the opposite or parallel line.

Curves.--The degree of curvature of a railway curve is generally expressed by giving the radius in feet, chains, metres, or other national standard measure.

When laying out a line of railway, the natural features of the country will necessitate the introduction of curves, and the question for consideration will be whether they are to be made of small or large radius. In some cases sharp curves are inevitable, except by incurring 50 enormous works which would not appear to offer any corresponding prospective recompense. In others the curves may be made of easy radius, at a comparative moderate extra outlay, if the character of the line and description of traffic to be accommodated will warrant the expenditure. For main through lines, with heavy, high-speed traffic, it is advisable to have the curves of large radius, so as to avoid the necessity of reducing speed when passing round them. Although a high-class fast train may be allowed to run round an 80 chain (5280 feet) curve at almost unrestricted speed, safety demands that there should be a reduction of speed on curves of 40 or 30 chains radius, and a very much greater reduction for curves of 20 chains radius and under. A sharp curve will in some places form a greater check to fast trains than a length of moderately steep gradient on a straight line. In the former the trains running in either direction must slow down for some distance before reaching the curve, round which they should pass at greatly reduced speed, and then some distance must be run before they can attain their full speed again. On the other hand, with a rising gradient, on a fairly straight line, the acquired momentum of the train will materially assist in ascending the incline, and although the speed may be slackened as the train advances, there may not be any very great diminution in the running before the gradient is passed, and average level line reached again. A reduced rate of running must be maintained round curves of small radius, for, however substantial the works and permanent way, and however well devised and constructed the rolling-stock, there is an element of danger ever present when passing round sharp curves at anything more than moderate speed. In the great rush for fast through trains this point is very apt to be overlooked, and too little time allowed for the running. Even with the fastest trains on any line there are some portions of the route which must be traversed with greater caution and less speed than others, either on account of sharp curves or of gradients; and if those who are entrusted with the preparations of the time tables do not possess the technical information necessary to deal properly with the question of relative speeds, there is the strong probability that the programme prepared may be one both difficult and dangerous to fulfil. The spirit of rivalry is a strong incentive to fast running, but prudence and common sense should indicate that record speeds should only be attempted on 51 the straight or favourable portions of the line. There is, unfortunately, the growing tendency to run faster and faster round the curved portion of our lines, heedless of the close approach to the limit of safety, and unless this excessive speed be controlled in time, the result must be disaster on a very large scale.

A sharp curve leading into or out of a terminal station or main-line stopping-station does not so much affect the train running as a sharp curve at an intermediate point between stations where the train may be expected to run at its maximum speed. Wherever it is possible it is very desirable to avoid sharp curves on inclines, because there are times when descending trains may acquire a considerable velocity, and wheels tightly gripped by the brakes have not the same facility for following the curves as when they are running free.

In rugged and mountainous districts sharp curves are almost unavoidable, except by introducing a series of tunnels; but in these districts both the gradients and curves are alike exceptional, the speed is necessarily slow, and special precautions are taken for the ascending and descending trains.

When setting out reverse curves on a main line a piece of straight line should always be laid in between the termination of the one curve and the beginning of the other, to allow of a proper adjustment of the rails to suit the super-elevation adopted on each of the adjoining curves. In station yards and sidings this is not so absolutely necessary, the sorting of the carriages and waggons and the marshalling of the trains being carried on at a low speed, which does not necessitate any super-elevation of the rails on the curves. The speed of the train regulates the amount of super-elevation to be given on any particular curve, and to ensure smooth and safe running this amount must be maintained uniform all round the curve. On curves of small radius, guard, or check, rails are frequently placed alongside the inner rail, as in Figs. 30 to 33, to check the tendency of the engine to leave the rails and run in a straight line. For the bull-head road a special chair is used, which holds both the running-rail and the check-rail, as shown on the sketch, the rails being kept the proper distance apart by the web portion in the centre, which forms part of the casting. For the flange railroad, check-rails are sometimes made of strong angle irons placed against the flange of the running-rail, and bolted to the transverse sleepers. This method 53 is not nearly so strong or efficient as the arrangement shown on Fig. 33, with a cast-iron distance-block about six inches long, placed between the running-rail and check-rail, and all tied together with a strong through bolt. A bolt-hole is punched in the edge of the flange of check-rail, and a crab bolt and clip holds the two rails on the sleeper. The cast-iron distance-blocks are placed just outside the sleeper, so as not to interfere with the holding-down bolt. Doubtless these guard rails do good service, but if the leading wheels of the engine have sharp or worn flanges there is the possibility that the wheel, pressing against the high rail, may mount the rail, and throw the train off the line. A more secure method is to place the guard outside the high rail, as in Figs. 34 to 38. This can be done by securing a strong continuous longitudinal timber to the cross-sleepers--or to the cross-girders in the case of a girder bridge--with its outer or striking edge protected with a fairly heavy angle iron. The top of this outside guard above the rail level may be three inches or more, according to the height of any hanging spring, or portion of brake apparatus belonging to the rolling-stock. The distance between the striking-face of the guard and the inside of head of rail should be about 5 inches, or such width that before the flange of the wheel can mount on the top of the rail, the face of the wheel-tyre will be brought into contact with the striking-face of the outside guard, and thus effectually prevent the wheel leaving the rail. The sketches show some of the types applicable to the chair road, and to the flange railroad. In Figs. 34, 35, and 37, the outside brackets are of heavy angle iron cut off in lengths to correspond to the width of the sleeper. In Fig. 36 the cast-iron chair is lengthened, and has an end bracket to support the guard timber. In Fig. 37 a hard wood bolster is fastened on the top of each sleeper, and on this is placed the continuous guard timber. This method of increased security is frequently adopted on girder bridges and long iron viaducts which are on the straight, and in such cases it is usual to place the guards outside each of the rails forming the track.

The introduction of bogie engines and bogie carriages has conduced largely to the safe working of the train-service over the curved portions of many of our home railways, as well as to the economy in the wear and tear of permanent way and rolling-stock. The action of long rigid wheel-base vehicles passing round sharp curves is 54 detrimental to all the parts brought into contact. Not only is there the constant tendency to mount the rails, and spread the gauge, but the tiny shreds of steel scattered all along close to the rail--particles ground off the rails, or off the wheel-tyres, or both--testify to useless wear, unnecessary friction, and great waste of motive-power.

The gradual increase of accommodation and conveniences in the carriage stock of European railways led to the gradual increase in the length of the vehicles. The six-wheeled carriage superseded the four-wheeled carriage, on account of its increased steadiness when running, but the introduction of long sleeping-cars, dining-cars, and corridor cars necessitated some better wheel arrangement than the ordinary six-wheel type could supply. The six wheels had been spread as far apart as was admissible for carrying weight and passing round curves, and something had to be done to meet the demand for still longer carriages. Many of the six-wheeled carriages at present running on our own home lines have a fixed wheel-base as long as 22 feet, and with this length the horn-plates must undergo a very considerable strain when adapting themselves for the passage round curves of small radius. On a curve of 15 chains radius (990 feet) a chord of 22 feet will have a versed sine or offset of 0·73 of an inch, and on a curve of 10 chains radius (660 feet) an offset of 1·10 of an inch. Fortunately, curves of the above small radius are not very numerous on our main lines; but wherever they do occur, the conflict between the long fixed wheel-base rolling-stock and the permanent way must be very severe to both. Several descriptions of eight-wheeled carriages have been tried on our home lines; but the system which is now most in favour is the ordinary bogie truck, which has been in use for so many years on all American railways. A bogie truck is really a short carriage frame complete in itself, with its wheels, springs, and brake appliances, and is attached to the under side of the carriage body by a central pivot, round which the truck can swivel or rotate sufficiently to adapt itself to the curved portions of the line. With a bogie truck at each end of a long carriage, the vehicle will pass as easily round curves as on the straight line, side pressure, or grinding against the rails, is obviated, and friction is reduced to a minimum. The bogie truck may consist of four wheels or six wheels, according to the length and weight of the carriage to be supported.

Figs. 39, 40, and 41 show sketch elevation, plan, and transverse 56 section of one pattern of four-wheel bogie truck largely adopted in American carriage stock, and although there are other types varying in detail, the general principle remains the same in all. The diagram sketch (Fig. 42) represents the two bogie trucks slightly swivelled to adapt themselves to the curve round which the carriage is supposed to be passing.

For carriage or waggon stock with an independent bogie truck at each end, the central pivot and swivelling motion supply all the freedom that is requisite; but for locomotives it is necessary to provide for lateral as well as for swivelling movement. The driving and trailing wheels--and sometimes one or two other pairs of wheels--work rigidly in the frames, and as the normal position of the centre of the bogie truck must be in the centre line of the engine for the straight line, it is evident that some appliance must be introduced to allow the truck to move laterally when the engine has to traverse the curves.

Figs. 43, 44, and 45 give sketch elevation, plan, and transverse section of a swing-link bogie truck as applied to an ordinary American locomotive. Its recommendations are its simplicity, its efficiency, and its accessibility for inspection and lubrication. The swing-links, which provide for the lateral movement, are direct acting, and do not require any side springs of steel or indiarubber. All the principal parts of the bogie are visible and not mysteriously cased in with plate-iron boxwork.

In the sketches several minor details are purposely omitted and only sufficient particulars shown to explain the method of working. The under side of the upper centre plate which carries the cylinder castings and smoke-box end of boiler is cup-shaped, and fits into an annular groove or channel in the lower centre plate, which is suspended from the framework of the truck by the four swinging links. Practically the entire carrying and swivelling work of the bogie truck is effected by the annular-groove casting moving round the cup-shaped casting, and the centre pin is merely passed down through each to guard against the risk of the one lifting out of the other from sudden shock or derailment.

The lateral movement of the truck is obtained by means of the four swing-links. When the engine is on the straight road the centre line of the bogie is on the centre line of the engine, and the links hang in the positions shown on the sketch, inclined towards the centre; but 58 upon entering a curve they come into play, and allow the truck to move out sideways to the right or left, according to the direction of the curve, the one pair of links assuming a flatter angle, while the other pair approach nearer to the vertical, the extent of side movement depending on the amount of the curvature. When the engine enters the straight line again, the bogie truck resumes its central position.

The Bissell truck consists of one pair of wheels connected to a triangular framework, as shown in Fig. 46. The axle-boxes are attached to the side of the triangle which lies parallel to the axle, the other two sides terminate in a circular ring which works round a centre pin fixed to the engine. These two sides are practically the radii of a given circle, and permit a large amount of lateral movement, which can be controlled by placing suitable stop-pieces to limit the side play to the extent desired.

Radial axle-boxes have been tried on the engines of some railways. In the best types the opposite boxes are braced together by a diaphragm, or plate-iron framework, to ensure that both boxes work together. The curved faces of the horn-blocks, in which the radial axle-boxes slide, are struck from a centre taken at some point to the rear of the normal centre line of the axle, and stops are placed at proper distances to control the extent of lateral movement. Although the advocates of radial axle-boxes may urge some points in their favour, there are few engineers, if any, amongst those who have had practical experience of both systems, who would for a moment claim for the radial axle-box anything but a modicum of the many advantages obtained by the four-wheeled bogie truck.

As one of the principal functions of a four-wheeled bogie truck for an engine is to act as a path-finder, or guide, to the other wheels which constitute the fixed or rigid wheel-base portion of the machine, it follows, therefore, that the full benefit of the bogie truck can only be obtained when it is placed at the leading, or front, end of the engine. In this position the bogie, with its swivelling arrangement and smaller weights, is the first to pass over the rails, and in doing so shapes the course and prepares the way for the easy running of the heavier wheel weights which have to follow. When the bogie truck is placed at the rear end of the engine, its action is restricted to affording lateral movement only, and the driving and coupled wheels have to force or pound themselves round the curves in a jerky, irregular manner, as compared to their smooth running when following 59 the leading or guiding influence of a bogie truck in front.

The wheel-base of a four-wheeled bogie truck for an engine should always be greater than the gauge of the line over which the bogie has to travel On the 4 feet 8½ inch gauge some of the best results have been obtained with bogies having wheel-bases varying from 6 feet to 7 feet. Where the wheel-centres have been less than 6 feet, the running has been found to be much less steady than with the wider spacing; and where the wheel-base is not more than the gauge, there is a tendency for the bogie to catch, or lock, when passing round sharp curves.