THERE are many objects on the railway seen by a passenger in a train with the uses of which he may not be familiar. On this page the functions of certain of the commonest of these are explained.

At every quarter-mile along all railway routes in Great Britain mile-posts are erected ; this is enjoined by law, for the mile-posts provide the measured basis on which fares are charged. As with milestones on the roads, the railway mile-posts are calculated from one zero point, which, so far as main lines are concerned, is generally London.

There is considerable variation in both the design and location of mile-posts, and three different varieties are illustrated on this page, namely, those of the late Midland and London and North Western Railways (both now part of the L.M.S.) and of the Great Western Railway. The Midland type of quarter-mile post displays the relative mile as well as the fraction, and both mile-posts and quarter-posts have their indications on two sides of an angle, so that they may be readily seen when approached from either direction.

The Great Western type of post is similar, but it is ingeniously designed in such a way that the mile forms the upper part of the indication, the quarter, half, or three-quarters being shown by means of one, two, or three vertical strokes underneath. On the Western Division of the L.M.S. (late London and North Western Railway), the quarter-posts do not show the relative mile, but merely the figures "1/4," "1/2," and "3/4." This is also the general practice on other lines.

On the Western Division of the L.M.S. the mile-posts are found, with one or two isolated exceptions, on the down side of the line. Starting from zero at Euston, they continue to the 188 th mile-post, just beyond Golborne Junction, north of Warrington, after which a new series, again starting at zero, runs as far as Preston, 209 miles from Euston. There is a third series beginning at Preston and running to Lancaster, twenty-one miles from Preston. A fourth series starts from zero at Lancaster and ends at Carlisle, sixty-nine miles from Lancaster. Beyond Carlisle the old Caledonian posts begin, and starting from zero at Carlisle, continue exclusively on the down side, to Glasgow, Edinburgh, and Aberdeen.

A SIGNAL GANTRY viewed from a signal-box at Reading on the Great Western Railway, showing home and distant signals. On the right is a home signal with a miniature "calling-on" arm underneath. The man at the window is "checking" trains as they pass and noting the times of their passing the box. The signals are of the "lower quadrant" type.

The mile-posts of the Midland Division, which are the largest and most easily seen of any in Great Britain, are all on the up side of the line, and form one uninterrupted sequence from zero at St. Pancras to Carlisle.

On the Great Northern Section of the L.N.E.R., the down side of the line is favoured, and the posts run through from zero at King's Cross to York. From here, over the North Eastern Area, there is one series from York to Newcastle, and another from Newcastle to Berwick, all on the down side. But a change is then made to the posts of the Scottish Area, which are measured from zero at Edinburgh (Waverley), and are all on the left side of the line leading from Waverley, which is, of course, the present up side between Berwick and Edinburgh.

The Great Western Railway favours the up side of the line, and the Western Section of the Southern Railway (the late London and South Western Railway) the down side. All the Great Western series follows the original routes; this leads to some curious mile-post readings on a journey, say, from Paddington to Penzance From London to Westbury the posts are in direct sequence, via Reading and Savernake. From Westbury to Castle Cary the posts are marked in accordance with the original Weymouth route, from Paddington via Swindon and Trowbridge. Then comes a resumption of the direct London distances, from Castle Cary to Cogload, where the series from London via Bath and Bristol is joined ; this continues for the remainder of the journey.

The speed restriction signs, illustrated on this page, require some explanation. The one marked "25" indicates a permanent speed restriction to twenty miles an hour. Next come the movable signs used in connexion with track relaying and other permanent way work. First is the green board, fixed, similarly to a distant signal, half a mile away from the site of the speed restriction, and displaying white and green lights at night, side by side. Then comes the "C," or "Commences" sign, where the speed restriction begins, followed by the "T," or "Terminates" sign, at the point where normal speed may be resumed. All these signs are illuminated at night, and frequently the figure to which speed must be reduced is now also displayed at the outer "caution" sign.

The "levelling post" shown at the right hand side of the series of diagrams is generally found as one of a series erected at the line-side where subsidence trouble is being experienced, especially in colliery areas. These posts are installed at intervals with their graduated divisions exactly in line, so that it is readily possible to detect by eye if any one post in the series has subsided.

At the bottom of the diagrams are seen, on the left, the type of warning board used on the Great Northern Section of the L.N.E.R. to indicate to drivers the beginning of water-troughs. Other main lines have a variety of similar trough indications, but some give no warning of this description. The corresponding plain board on the right-hand side is displayed immediately in advance of the ground apparatus for the exchange of mails to warn the postal officials on the mail trains to be in readiness if exchange is about to be made.

Between these are seen two varieties of gradient posts, which indicate the changes of gradient. An upward tilt of the indicator shows, of course, the beginning or end of an up gradient, and a downward tilt a down gradient. On some lines the full "1 in 200," or whatever the gradient may be, is inscribed ; on others merely the significant figure "200." On certain routes, such as the Great Eastern Section of the L.N.E.R., the infinity sign is used instead of the word "level," where level track is indicated.

TO GUIDE THE ENGINE-DRIVER such indications as these are placed by the side of the railway lines in Great Britain. Mile-posts vary considerably in design and position. The figure "25" on the permanent speed restriction indicator shows that 25 miles an hour must not be exceeded. A temporary speed restriction begins with a board marked "C" and ends with one marked "T." The levelling post is generally found where subsidence trouble is being experienced, particularly in mining districts. The posts, installed at intervals, with their divisions exactly in line, reveal any depression of the ground.

The second series of diagrams explains the arrangement of the headlamps carried on the front of locomotives on most of the railways in Great Britain. Readers will probably have noticed that lamps are mounted in this way by day as well as by night. The object is for these lamps to indicate to signalmen and others concerned with the working of the traffic the exact nature of each train.

In the national headcode the positions used are four only. One is at the base of the engine chimney, either on the top of the smoke-box, or—now that the upper level of the boiler is often so high and the chimney so short—at the top of the smoke-box door. Two more are at either end of the buffer-beam, and the fourth position is in the centre of the buffer-beam. In the normal course the lamps used show white lights only, and on the L.N.E.R. the lamps themselves are painted white, so that they may be the more easily seen in the daytime.

Of all the headlamp indications, probably the most familiar is the pair of white lights, one over either buffer, which indicates "Express Passenger Train." Then there is one single light at the base of the chimney, indicating "Ordinary Stopping Passenger Train." Other indications, for freight trains of various kinds, light engines, and empty coach trains, are explained on the diagrams. The only code requiring the use of all four lamp-irons at once is "Royal Special Train."

On the Southern Railway, however, the complexity of routes is such that the lamps are used to indicate the route that each train is to follow, rather than the description of the train. Further, in the daytime, for ready recognition, the lamps are replaced by circular sheet metal disks, painted white. Some of the best-known main-line route indications on the Southern are shown in the diagrams, from which it will be seen that there are six lamp positions, instead of four only, on Southern locomotives.

In addition to the four positions of the national headcode, there are lamp and disk positions on either side of the smoke-box, affording a notably wide variation in the indications. Continental express trains from Victoria to Dover carry their lamps in the "Express Passenger" position ; express trains from Waterloo to Salisbury and the West carry their lamps in a vertical line, one at the base of the chimney, and one in the centre of the buffer-beam.

On the Great Eastern Section of the L.N.E.R. also, disks are used in the day-time, on the main lines and country branches in accordance with the national headcode, and in the London suburban area for route indicating purposes, as on the Southern. On these Great Eastern lines blue lights as well as white lights are employed, replaced in the day-time by blue disks with white rims. There are certain other routes in Great Britain over which disks are used for indicating purposes of one kind and another.

In Scotland an ingenious type of route indicator is employed on the Caledonian and Glasgow and South Western Sections of the L.M.S. It consists of a frame with two movable arms, painted white, which can be altered in the manner of the hands of a clock. Most familiar of all its positions, probably, is with the two arms set horizontally, at "a quarter to three," which indicates the main line from Glasgow to Carlisle via Carstairs. The engine of the "Royal Scot," if working through from Glasgow to London, is often seen arriving at Euston with its Scottish indicator, at the base of the chimney, set in this position.

THESE DIAGRAMS INDICATE: 1. Express passenger train; breakaown train going to clear line ; or light engine going to assist disabled train. 2. Ordinary passenger train ; or breakdown train not going to clear line. 3. Empty coaching stock train ; express fish, meal, fruit, or other train carrying "perishable" traffic, or horse and cattle train, composed of coaching vehicles fitted with the continuous brake. 4. Fish, meat, or fruit train, or express cattle or express freight train composed of freight stock. Class "A" (speed, 30 miles an hour). 5. Express cattle or express freight train, Class "B" (speed, 20 miles an hour). 6. Light engine or engines ; or engine with brake-van, 7. Through freight, mineral, or ballast train, not booked to make intermediate stops, Class "C" (speed, 20 miles an hour). 8. Through freight train, making intermediate stops. 9. Ordinary freight train, calling at intermediate stations. 10. Royal special train. 11. Waterloo, Salisbury, Exeter, and Plymouth. 12. Waterloo and Portsmouth via Guildford. 13. Waterloo, Southampton and Bournemouth West via Sway. 14. Victoria, Folkestone, and Dover via Orpington loop; Victoria and Newhaven Harbour. 15. Waterloo and Southampton Docks (special boat trains).

Below is a set of diagrams explaining the meanings of signals and ground disks, and certain of their variations which are most widely used. At the top left hand side appear home and distant signal-arms on one post. The second and third of these diagrams show the older "lower quadrant" type of semaphore arm, in which the arm drops when pulled to the "clear" position. Except on the Great Western Railway, this type is now being replaced by the "upper quadrant" type, in which the arm rises when pulled off.

The substitution is chiefly for purposes of economy. Provision must be made for the signal to return automatically to "danger" in the event of any breakage of its operating mechanism.

The lower quadrant arm had therefore to be provided with a heavy spectacle casting, holding the red or yellow and green glasses that move in front of the lamp, to provide a "balance" that would return the arm to danger should the rod from the base of the post break or become disconnected. But such a breakage, with an upper quadrant arm, would simply result in the arm falling to danger by its own weight, and a much lighter and more economical spectacle casting thus serves the purpose.

With both home and distant signals "on," "danger" is indicated, and the train must stop. The home signal "off" and the distant signal "on" indicate that only one block section ahead is clear, and instructs a driver to "proceed with caution." Both home and distant signals pulled off show that two or more sections ahead are clear, and permit the driver to "proceed at full speed."

The upper, or home signal arms are square at the outer ends, and are painted red with white stripe on the side facing the driver ; at night they display a red light for "danger," and a green light for "clear." The lower or "distant" signal arms are painted yellow, with a black stripe, and display at night an orange light when "on," and a green light when "off." Provision is made by locking, by means of a "slot" on the post itself, to ensure that the distant arm cannot be pulled off unless the home arm is also off, and to return the distant arm to danger when the home arm returns to danger, even though the balance weight of the former is still pulled off.

The corresponding indications with colour-light electric signals are red for danger, yellow for one section ahead clear ("caution"), and green for two or more sections ahead clear ("full speed"), except where, on very densely-occupied routes, the double yellow indication is in use, when two yellow lights show two sections ahead clear, and green shows three or more sections ahead clear.

Reverting to the third set of diagrams, at the right-hand end there are shown types of miniature or subsidiary signals which permit a driver to draw past a home signal at danger, though not to leave the section. The short arm with a horizontal white stripe is a "draw-ahead" signal, often used, for example, at stations to enable a train to draw in to the rear end of a platform when the front end is already occupied with another train. The short arm marked "S" is used on the Great Western Railway and indicates "Shunt" ; it indicates to a driver that he is to shunt back into a siding.

In the centre of the diagrams the arm made in the shape of a cross is another variety of "draw ahead" signal ; and the arm with two holes in is in use on the Great Western Railway to permit a train to "set back"—that is, travel for a short distance in the wrong direction to the flow of traffic—along a running line.

Along the bottom of this diagram, at the left-hand end, there first appears a "banner" signal, in both the "on" and "off" positions. This is electrically worked, and its use is normally confined to busy routes only ; customarily it "repeats," automatically, the position of the next stop signal ahead, which by reason of curves or other obstructions cannot be seen until the train is closely approaching it.

In the centre of the bottom row of diagrams are seen "ground disks," which are fixed at ground level, and used to control shunting movements only. The low location is so that there shall be as little confusion as possible with the "running signals" controlling the through running. The new standard type of ground disk is on the left, in both the "on" position, when it displays a small white light, and in the "off," when it shows green. The disk itself is painted white, with a red bar across. The older type, on the right, is a disk that rotates, showing a red face with a small white light when "on," and a green side, with a green light, when "off."

The last two diagrams, in the lower right-hand corner, are connected with the all-important "track circuit," whereby the whole of the track in the vicinity of a signal-box is electrified, and any train, engine, or vehicle standing in the area so controlled, by providing a short circuit between the rails, advertises its presence on an indicator in the box, and imposes a lock on the signal lever controlling admission to the section on which it is standing.

Now if a train is brought to a stand for any appreciable time at a home or starting signal, Rule 55 of the Rules and Regulations requires the fireman to proceed to the signal box so that the presence of the train may not be overlooked. This is not necessary, however, if track circuit is in use, and if the line is track-circuited, a white diamond is fixed to the signal-post, as shown, below the signal-arm concerned. More infrequently, and especially if several tracks have to be crossed to reach the box, a telephone is provided at the signal-post so that the fireman may get into communication with the signalman in this way ; and the existence of the telephone is then announced to the driver by the white loop affixed to the post in the same position as the white diamond.

On the former Great Northern Railway, now part of the L.N.E.R., the "somersault" type of signal arm was used. This was pivoted in the centre instead of at the end. When the "somersault" signal was "off," it stood in a vertical position, away from the post.

This type of signal was introduced as a safety measure after an accident at Abbots Ripton, Hunts, in 1876. In that year the slot of a signal of the normal type had become blocked with snow during a blizzard and the signal did not return to the danger position when the lever was released.

Another unusual type is the three-position signal, used extensively in the U.S.A., and formerly to a limited extent around London.

THE INDICATIONS of various signals which are common over Great Britain are denoted in the diagrams. The use of the upper quadrant type is rapidly becoming more widespread, as it is of lighter construction and offers a greater guarantee of safety, for in the event of an accidental disconnection or break in the signal mechanism the arms drop to the horizontal or "danger" position.

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