A SHIP-RAISING LIFT
The writer has treated one form of lift for raising ships out of the water—the floating dry dock—elsewhere,[21] so his remarks in this place will be confined to mechanism which, having its foundations on Mother Earth, heaves mighty vessels out of their proper element by the force of hydraulic pressure. Looking round for a good example of an hydraulic ship-lift, we select that of the Union Ironworks, San Francisco.
Some years ago the works were moved from the heart of the city to the edge of Mission Bay, with the object of carrying on a large business in marine engineering and shipbuilding. For such a purpose a dry dock, which in a short time will lift a vessel clear of the water for cleaning or repairs, is of great importance to both owners and workmen. By the courtesy of the proprietors of Cassier's Magazine we are allowed to append the following account of this interesting lift.
The site available for a dock at the Union Ironworks was a mud-flat. The depth of soft mud being from 80 to 90 feet, would render the working of a graving dock (i.e. one dug out of the ground and pumped dry when the entrance doors have been closed) very disagreeable; as such docks, where much mud is carried in with the water, require a long time to be cleaned and to dry out. Plans were therefore prepared by Mr. George W. Dickie for an hydraulic dock, including an automatic control, which the designer felt confident would meet all the requirements of the situation, and which, after careful consideration, the Union Ironworks decided to build. Work was begun in January, 1886, and the dock was opened for business on June 15th, 1887—a very fine record.
This dock consists of a platform built of cross and longitudinal steel girders, 62 feet wide and 440 feet long, having keel blocks and sliding bilge blocks upon which the ship to be lifted rests. The lifting power is generated by a set of four steam-driven, single-acting horizontal plunger pumps, the diameter of the plungers being 3 1 / 2 inches and the stroke 36 inches. Forty strokes per minute is the regular speed.
There is a weighted accumulator, or regulator, connected with the pumps, the throttle valve of the engines being controlled by the accumulator.[22] The load on the accumulator consists of a number of flat discs of metal, the first one about 14 inches thick and the others about 4 inches thick, the diameter being about 4 feet. The first disc gives a pressure of 300 lbs. per square inch. This is sufficient to lift the dock platform without a ship, and is always kept on.
In lifting a ship, as she comes out of the water and gets heavier on the platform, additional discs are taken on by the accumulator ram as required. The discs are suspended by pins on the side catching into links of a chain. The engineer, to take on another disc, unhooks the throttle from the accumulator rod, runs the engine a little above the normal speed, the accumulator rises and takes the weight of the disc to be added; the link carrying that disc is thus relieved and is withdrawn. The engineer again hooks the accumulator rod to the engine throttle, and the whole is self-acting again until another weight is required. When all the discs are on the ram the full pressure of 1,100 lbs. per square inch is reached, which enables a ship of 4,000 tons weight to be raised.
There are eighteen hydraulic rams on each side of the dock. These rams are each 30 inches in diameter and have a stroke of 16 feet; and as the platform rises 2 feet for 1 foot movement of the rams, the total vertical movement of the platform is 32 feet. When lowered to the lowest limit there are 22 feet of water over the keel blocks at high tide.
The foundations consist of seventy-two cylinders of iron, which extend from the top girders to several feet below the mud line. These cylinders are driven full of piles, no pile being shorter than 90 feet. The cylinders are to protect the piles from the teredo (the timber-boring worm), which is very destructive in San Francisco Harbour. A heavy cast-iron cap completes each of the foundation piers, and two heavy steel girders extend the full length of the dock on each side, resting on the foundation piers and uniting them all longitudinally. The hydraulic cylinders are carried by large castings resting on the girders, each having a central opening to receive a cylinder, which passes down between the piers. There are thirty-six foundation piers, and eighteen hydraulic cylinders on each side of the dock.
On the top of each hydraulic ram is a heavy sheave or pulley, 6 feet in diameter, over which pass eight steel cables, 2 inches in diameter, making in all 288 cables. One end of each cable is anchored in the bed-plates supporting the hydraulic cylinders, while the other end is secured to the side girders of the platform. Each of the cables has been tested with a load of 80 tons, so that the total test load for the ropes has been 21,000 tons.
In lifting a ship the load is never evenly distributed on the platform. There is, in fact, often more than one ship on the platform at once. Some rams, therefore, may have a full load and others much less. Under these conditions, to keep the platform a true plane, irrespective of the irregular distribution of the load, Mr. Dickie designed a special valve gear to make the action of the dock perfectly automatic. Down each side of the dock a shaft is carried, operated by a special engine in the power house. At each hydraulic ram this shaft carries a worm, gearing with a worm-wheel on a vertical screw extending the full height reached by the stroke of the ram. This screw works in a nut on the end of a lever, the other end of which is attached to the ram. Between the two points of support a rod, working the valves—also carried by the ram—engages with the lever. If at a given moment the screw-end is raised, say, six inches, the lever opens the valve. As the ram rises, the lever, having its other end similarly lifted by the rise, gradually assumes a horizontal position, and the valve closes.
To lift the dock the engine working the valve shaft is started, and with it the operating screws. These, through the levers, open the inlet valves. The rams now begin to move up: if any one has a light load it will move up ahead of the other, but in doing so it lifts the other end of the lever and closes the valve. In fact, the screws are continually opening the valves, while the motion of the rams is continually closing them, so that no ram can move ahead of its screw, and the speed of the screw determines the rate of movement of the lifting platform.
To lower the dock, the engine operating the valve shaft is reversed, and the screws and levers then control the outlet valves as they controlled the inlet valves in raising. When the platform has reached the limit of its movement, a line of locks on top of the foundation girders, thirty-six on each side, are pushed under the platform by an hydraulic cylinder, and the platform is lowered on to them, where it rests until the work is done on the ship; then the platform is again lifted, the locks are drawn back, and the platform with its load is lowered until the ship floats out. All the operations are automatic.
Since the dock was opened well over a thousand ships have been lifted in it without any accident whatever; the total register tonnage approaching 2,000,000. The great favour in which the dock is held by shipowners and captains is partly due to the fact already mentioned, that the ship is lifted above the level of tide water, where the air can circulate freely under the bottom, thus quickly taking up all the moisture, and where the workmen can carry on operations with greater comfort.
When extensive repairs have to be undertaken on iron or steel vessels, the fact that this dock forms part of an extensive shipbuilding plant, and is located right in the yard, enables such repairs to be executed with despatch and economy. Several large steamships have had the under-water portions of their hulls practically rebuilt in this dock. The steamship Columbia, of the Oregon Line, had practically a new bottom, including the whole of the keel, completed in twenty-six days. This is possible, because every facility is alongside the dock and the bottom of the vessel is on a level with the yard.
This being the only hydraulic dock controlled automatically (in 1897), it has attracted a large amount of attention from engineering experts in this class of work. English, French, German, and Russian engineers have visited the Union Iron Works to study its working, and their reports have done much to bring the facilities offered to shipping for repairs by the Union Iron Works to the notice of shipowners all the world over.
FOOTNOTES:
[21.] The Romance of Modern Engineering, pp. 383 foll.
[22.] For explanation of the "accumulator," see the chapter on Hydraulic Tools ([p. 81]).
[CHAPTER XXI]
A SELF-MOVING STAIRCASE
At the American Exhibition, held in the Crystal Palace in 1902, there was shown a staircase which, on payment of a penny, transported any sufficiently daring person from the ground-floor to the gallery above. All that the experimenters had to do was to step boldly on, take hold of the balustrade, which moved at an equal pace with the stairs, and step off when the upper level was reached.
The "escalator" (Latin scalae = flight of stairs) hails from the United States, where it is proving a serious rival to the elevator. In principle, it is a continuously working lift, the slow travel of which is more than compensated by the fact that it is always available. The ordinary elevator is very useful in a large business or commercial house, where it saves the legs of people who, if they had to tramp up flight after flight of stairs, would probably not spend so much money as they would be ready to part with if their vertical travel from one floor to another was entirely free of effort. But the ordinary lift is, like a railway, intermittent. We all know what it means to stand at the grille and watch the cage slide downwards on its journey of, perhaps, four floors, when we want to go to a floor higher up. Rather than face the delay we use our legs.
Theoretically, therefore, a large emporium should contain at least two lifts. If the number be further increased, the would-be passenger will have a still better chance of getting off at once. Thus at the station of the Central London Railway we have to wait but a very few seconds before a grille is thrown back and an attendant invites us to "Hurry up there, please!"
Yet there is delay while the cage is being filled. The actual journey occupies but a small fraction of the time which elapses between the moment when the first passenger enters the lift at the one end of the trip and the moment when the last person leaves it at the other end. In a building where the lift stops every fifteen feet or so to take people on or put them off, the waste of time is still more accentuated.
The escalator is always ready. You step on and are transported one stage. A second staircase takes you on at once if you desire it. There is no delay. Furthermore, the room occupied by a single escalator is much less than that occupied by the number of lifts required to give anything like an equally efficient service.
In large American stores, then, it is coming into favour, and also on the Manhattan Elevated Railway of New York. When once the little nervousness accompanying the first use has worn off, it eclipses the lift. A writer in Cassier's Magazine says: "In one large retail store during the holiday season more than 6,000 persons per hour have been carried upon the escalator for five hours of the day, and the aggregate for an entire day is believed to be 50,000. In the same store on an ordinary day the passengers alighting at the second floor from the eight large lifts, which run from the basement to the fifth floor, were counted, likewise the number at the escalator. This latter was found to be 859 per cent. of the number delivered by the eight lifts. In another establishment, in a very busy hour, the number taken from the first floor by the escalator was four times the number taken from the first floor by the fourteen lifts, which were running at their maximum capacity. To the merchant this spells opportunity for business.
"The experience at the Twenty-third Street and Sixth Avenue station of the Manhattan Elevated Railway in New York, during a recent shut-down of the escalator, which has been in service for some time, is interesting as showing the attitude of the public, of which many millions have been carried by the installation during the several years of its operation. The daily traffic receipts of this station for a period beginning several weeks before the shut-down and extending as many after, for the years 1903 and 1902, and receipts of the adjacent stations for the same period were carefully plotted ... and the loss area during the period of shut-down was determined. The loss area was found to embrace 64,645 fares. It was, furthermore, daily a matter of observation that numbers of people, finding that the escalator was not running, refused to climb the stairs, and turned away from the station.
"In the case of a great store, the escalator may be constructed as one continuous machine, with landings at each floor, and so arranged that steps which carry passengers up may perform a like service in carrying others down; or separate machines may be installed in various locations affording the best opportunity for displaying merchandise to the customer who may be proceeding from the lower to the upper floor. In the case of a six-storey building so equipped with escalator service in both directions, or in all ten escalator flights, it is obvious that the facilities are equal to an impossible number of elevators; and as facility of access has a direct bearing upon opportunities for business, it may well be argued that the relative value, measured by rent, of the main and upper floors is greatly changed."
Each step in a staircase has two parts—the "tread" or horizontal board on which the foot is placed, and the vertical "riser" which acts both as a support to the tread above and also prevents the foot from slipping under the tread. In the escalator each tread is attached rigidly to its riser, and the two together form an independent unit.
For the convenience of passengers in stepping on or off at the upper and lower landings, the treads in these places are all in the same horizontal plane. As they approach the incline the risers gradually appear, and the treads separate vertically. At the top of the incline the process is gradually reversed, the risers disappearing until the treads once more form a horizontal belt.
The means of effecting this change is most ingenious. Each tread and its riser is carried on a couple of vertical triangular brackets, one at each side of the staircase. The base of the bracket is uppermost, to engage with the tread, and its apex has a hole through which passes a transverse bar, which in its central part forms a pin in the link-chain by which power is transmitted to the escalator. Naturally, the step would tip over. This is prevented by a yoke attached to each end of the bar, at right angles to it and parallel to the tread. The yoke has at each extremity a small wheel running on its own rail—there being two rails for each side of the staircase.
Since step, brackets, bar, and yoke are all rigidly joined together, the step is unable to leave the horizontal, but its relation to the steps above and below is determined by the arrangement of the rails on which the yoke wheels run. When these are in the same plane, all the yokes, and consequently the treads, will also be in the same plane. But at the incline, where the inner rail gradually sinks lower than its fellow, the front wheel of one tread is lower than the front wheel of the next, and the risers appear. It may be added that, owing to the double track at each side of the staircase, the back wheel of one tread does not interfere with the front wheel of that below; and that on the level they come abreast without jostling, as the yoke is bent.
The chain, of which the step-bars form pins, travels under the centre of the staircase. It is made up of links eighteen inches long, having, in addition to the bars, a number of steel cross-pins 1 1 / 2 inches in diameter, their axes three inches apart, so that the chain as a whole has a three-inch "pitch." The hubs of the links are bushed with bronze, and have a graphite "inlay," which makes them self-lubricating. Every joint is turned to within 1 / 1,000 inch of absolute accuracy.
The tracks are of steel and hardwood, insulated from the ironwork which supports them by sheets of rubber. The wheels are so constructed as to be practically noiseless, so that as a whole the escalator works very quietly.
"It has been observed," says the authority already quoted, "that beginners take pains to step upon a single tread, and that after a little experience no attention whatever is given to the footing, owing to the facility of adapting oneself to the situation. The upper landing is somewhat longer, thereby affording an interval for stepping off at either side of sufficient duration to meet the requirements of the aged and infirm. The sole function of the travelling landing is to provide a time interval to meet the requirements of the slowest-acting passenger, and not of the alert. The terminal of the exit landing, be it top or bottom (for the escalator operates equally well for either ascent or descent), is a barrier, called the shunt, of which the lower member travels horizontally in a plane oblique to the direction of movement of the steps, and at a speed proportionately greater, thereby imparting a right-angle resultant to the person or obstacle on the step which may come in contact with the shunt. By reason of this resultant motion, the person or obstacle is gently pushed off the end of the step upon the floor, without shock or injury in the slightest degree. The motion of the escalator is so smooth and constant that it does not interpose the least obstacle to the free movement of the passenger, who may walk in either direction or assume any attitude to the same degree as upon a stationary staircase."
At Cleveland, U.S.A., there has been erected a rolling roadway, consisting of an inclined endless belt and platform made of planks eight feet long, placed transversely across the roadway. The timbers are fastened together in trucks of two planks each, adjoining trucks being joined by heavy links to form a moving roadway, which runs on 4,000 small wheels. At each end the roadway, which is continuous, passes round enormous rollers. Its total length is 420 feet, and the rise 65 feet. Four electric motors placed at regular intervals along its length, and all controlled by one man at the head of the incline, drive it at three miles an hour. It can accommodate six wagons at a time.
[CHAPTER XXII]
PNEUMATIC MAIL TUBES
You put your money on the counter. The shop assistant makes out a bill; and you wonder what he will do with it next. These large stores know nothing of an open till. Yet there are no cashiers' desks visible; nor any overhead wires to whisk a carrier off to some corner where a young lady, enthroned in a box, controls all the pecuniary affairs of that department.
While you are wondering the assistant has wrapped the coin in the bill and put the two into a dumb-bell-shaped carrier, which he drops into a hole. A few seconds later, flop! and the carrier has returned into a basket under another opening. There is something so mysterious about the operation that you ask questions, and it is explained to you that there are pneumatic tubes running from every counter in the building to a central pay-desk on the first or second floor; and that an engine somewhere in the basement is hard at work all day compressing air to shoot the carriers through their tubes.
Certainly a great improvement on those croquet-ball receptacles which progressed with a deliberation maddening to anyone in a hurry along a wooden suspended railway! Now, imagine tubes of this sort, only of much larger diameter, in some cases, passing for miles under the streets and houses, and you will have an idea of what the Pneumatic Mail Despatch means: the cash and bill being replaced by letters, telegrams, and possibly small parcels.
"Swift as the wind" is a phrase often in our mouths, when we wish to emphasise the celerity of an individual, an animal, or a machine in getting from one spot of the earth's surface to another. Mercury, the messenger of uncertain-tempered Jove, was pictured with wings on his feet to convey, symbolically, the same notion of speed. The modern human messenger is so poor a counterpart of the god, and his feet are so far from being winged, that for certain purposes we have fallen back on elemental air-currents, not unrestrained like the breezes, but confined to the narrow and certain paths of the metal tube.
The pneumatic despatch, which at the present day is by no means universal, has been tried in various forms for several decades. Its first public installation dates from 1853, when a tube three inches in diameter and 220 yards long was laid in London to connect the International Telegraph Company with the Stock Exchange. A vacuum was created artificially in front of the carrier, which the ordinary pressure of the atmosphere forced through the tube. Soon after this the post-office authorities took the matter up, as the pneumatic system promised to be useful for the transmission of letters; but refused to face the initial expense of laying the tube lines.
When, in 1858, Mr. C. F. Varley introduced the high pressure method, pneumatic despatch received an impetus comparable to that given to the steam-engine by the employment of high-pressure steam. It was now possible to use a double line of tubes economically, the air compressed for sending the carriers through the one line being pumped out of a chamber which sucked them back through the other. Tubes for postal work were soon installed in many large towns in Great Britain, Europe, and the United States; including the thirty-inch pneumatic railway between the North-Western District post office in Eversholt Street and Euston Station, which for some months of 1863 transported the mails between these two points. The air was exhausted in front of the carriage by a large fan. Encouraged by its success, the company built a much larger tube, nearly 4 1 / 2 feet in diameter, to connect Euston Station with the General Post Office. This carried fourteen tons of post-office matter from one end to the other in a quarter of an hour. There was an intermediate station in Holborn, where the engines for exhausting had been installed. But owing to the difficulty of preventing air leakage round the carriages the undertaking proved a commercial failure, and for years the very route of this pneumatic railway could not be found; so quickly are "failures" forgotten!
The more useful small tube grew most vigorously in America and France. In, or about, the year 1875 the Western Union Telegraph Company laid tubes in New York to despatch telegrams from one part of the city to the other, because they found it quicker to send them this way than over the wires. Eighteen years later fifteen miles of tubes were installed in Chicago to connect the main offices of the same company with the newspaper offices in the town, and with various important public buildings. Messages which formerly took an hour or more in delivery are now flipped from end to end in a few seconds.
The Philadelphia people meanwhile had been busy with a double line of six-inch tubes, 3,000 feet long, laid by Mr. B. C. Batcheller between the Bourse and the General Post Office, for the carriage of mails. The first thing to pass through was a Bible wrapped in the "Stars and Stripes." A 30 horse-power engine is kept busy exhausting and compressing the air needed for the service, which amounts to about 800 cubic feet per minute. Philadelphia can also boast an eight-inch service, connecting the General Post Office with the Union Railway Station, a mile away. One and a half minutes suffice for the transit of the large carriers packed tightly with letters and circulars, nearly half a million of which are handled by these tubes daily.
New York is equally well served. Tubes run from the General Post Office to the Produce Exchange, to Brooklyn, and to the Grand Central Station. The last is 3 1 / 2 miles distant; but seven minutes only are needed for a tube journey which formerly occupied the mail vans for nearly three-quarters of an hour.
Paris is the city of the petit bleu, so important an institution in the gay capital. Here a network of tubes connects every post office in the urban area with a central bureau, acting the part of a telephone exchange. If you want to send an express message to a friend anywhere in Paris, you buy a petit bleu, i.e. a very thin letter-card not exceeding 1 / 4 oz. in weight, at the nearest post office, and post it in a special box. It whirls away to the exchange, and is delivered from there if its destination be close at hand; otherwise it makes a second journey to the office most conveniently situated for delivery. Everybody uses the voie pneumatique of Paris, so much cheaper than, and quite as expeditious as, the telegraph; with the additional advantage that all messages are transmitted in the sender's own handwriting. The system has been instituted for a quarter of a century, and the Parisians would feel lost without it.
London is by no means tubeless, for it has over forty miles of 1 1 / 2 , 2 1 / 4 , and 3-inch lines radiating from the postal nerve-centre of the metropolis, of lengths ranging from 100 to 2,000 yards. The tubes are in all cases composed of lead, enclosed in a protecting iron piping. To make a joint great care must be exercised, so as to avoid any irregularity of bore. When a length of piping is added to the line, a chain is first passed through it, which has at the end a bright steel mandrel just a shade larger than the pipe's internal diameter. This is heated and pushed half-way into the pipe already laid; and the new length is forced on to the other half till the ends touch. A plumber's joint having been made, the mandrel is drawn by the chain through the new length, obliterating any dents or malformations in the interior.
The main lines are doubled—an "up" and a "down" track; short branches have one tube only to work the inward and the outward despatches.
The carriers are made of gutta-percha covered with felt. One end is closed by felt discs fitting the tube accurately to prevent the passage of air, the other is open for the introduction of messages. As they fly through the tube, the carriers work an automatic signalling apparatus, which tells how far they have progressed and when it will be safe to despatch the next carrier.
The London post-office system is worked by six large engines situated in the basement of the General Post Office.
So useful has the pneumatic tube proved that a Bill has been before Parliament for supplying London with a 12-inch network of tubes, totalling 100 miles of double line. In a letter published in The Times, April 19, 1905, the promoters of the scheme give a succinct account of their intentions, and of the benefits which they expect to accrue from the scheme if brought to completion. The Batcheller system, they write, with which it is proposed to equip London, is not a development of the miniature systems used for telegrams or single letters here or in Paris, Berlin, and other cities. Such systems deal with a felt carrier weighing a few ounces, which is stopped by being blown into a box. The Batcheller system deals with a loaded steel carrier weighing seventy pounds travelling with a very high momentum. The difference is fundamental. In this sense pneumatic tubes are a recent invention, and absolutely new to Europe.
The Batcheller system is the response to a pressing need. Careful observations show that more than 30 per cent. of the street traffic is occupied with parcels and mails. These form a distinct class, differentiated from passengers on the one hand and from heavy goods on the other. The Batcheller system will do for parcels and mails what the underground electric railways do for passengers. It has been in use for twelve years in America for mail purposes, and where used has come to be regarded as indispensable.
The plan for London provides for nearly one hundred miles of double tubes with about twice that number of stations for receiving and delivery. The system will cover practically the County of London, and no point within that area can be more than one-quarter of a mile from a tube station. Beyond the County of London deliveries will be made by a carefully organised suburban motor-cart service. Thirty of the receiving stations are to be established in the large stores. The diameter of the tube is to be of a size that will accommodate 80 per cent. of the parcels, as now wrapped, and 90 per cent. with slight adaptation. The remaining 10 per cent.—furniture, pianos, and other heavy goods—are to be dealt with by a supplementary motor service. If the tubes were enlarged their object would be partially defeated, for with the increased size would go increased cost, great surplus of capacity, less frequent despatch, and lower efficiency generally. The unsuccessful Euston Tunnel of forty years ago—practically an underground railway—is an extreme illustration of this point, though in that case there were grave mechanical defects as well.
From a mechanical point of view the system has been brought to such perfection that it is no more experimental than a locomotive or an electric tramcar. The unique value of tube service is due to immediate despatch, high velocity of transit, immunity from traffic interruption, and economy. The greatest obstacle to rapid intercommunication is the delay resulting from accumulations due to time schedules. The function of tube service is to abolish time schedules and all consequent delays.
The number of trades parcels annually delivered in London is estimated at more than 200,000,000. A careful canvass has been made of 1,000 shops only, which represent a very small fraction of the total number in the county. As a result it has been ascertained that these 1,000 shops deliver no fewer than 60,000,000 parcels yearly, a fact that seems to more than justify the foregoing estimate; on the other hand, it is known from official data that the parcel post in London is represented by less than 25,000,000, or one-ninth of the total parcel traffic. With a tube system in operation, every parcel, instead of waiting for "the next delivery," would leave the shop immediately. After being despatched by the tube it would be delivered at a tube station within a quarter of a mile at least of its destination, and thence by messenger. The entire time consumed for an ordinary parcel would be not over an hour, and for a special parcel fifteen to twenty minutes. They require from three to six hours or longer at present.
The advantages of the tube system to the public would be manifold. Customers would find their purchases at home upon their return, or, if they preferred, could do their shopping by telephone, making their selections from goods sent on approval by tube. The shopman would find himself relieved from a vast amount of confusion and annoyance, less of his shop space given up to delivery, and his expenses reduced. Small shops would be able to draw upon wholesale houses for goods not in stock, while the customer waited. Such delay and confusion as are frequently occasioned by fogs would be reduced to a minimum.
While the success of the project is not dependent on Post Office support, the Post Office should be one of the greatest gainers by it. The time of delivery of local letters would be reduced from an average of three hours and six minutes to one hour. Express letters would be delivered more quickly than telegrams. This has been demonstrated conclusively again and again in New York and other American cities where the tubes have been in operation for years. The latest time of posting country letters would be deferred from one-half to one hour, and incoming letters would be advanced by a similar period. The parcels post would gain in precisely the same way, but to an even larger extent.
If the Post Office choose to avail themselves of the opportunity, every post office will become a tube station and every tube station a post office. Thus the same number of postmen covering but a tithe of the present distances could make deliveries without time schedules at intervals of a few minutes with a handful instead of a bagful of letters.
The sorting of mails would be performed at every station instead of at a few. Incoming country mails would be taken from the bags at the railway termini, and the same bags refilled with outgoing country mails, thus avoiding needless carriage to the Post Office and back. No bags at all would be used for local mails, the steel carriers themselves answering that purpose.
At every tube terminal a post-office clerk would be stationed, so that the mails would never for an instant be out of post-office control. Its absolute security would be further ensured by a system of locking, so that the carriers could only be opened by authorised persons at the station to which they were directed. These safeguards offer a striking contrast to the present method that entrusts mail bags to the sole custody of van drivers in the employ of private contractors.
If the mails were handled by tube, business men would be able to communicate with each other and receive replies several times in one day, and country and foreign letters could always be answered upon the day of receipt. The effect would be felt all over the Empire.
Would the laying of the tubes seriously impede traffic? The promoters assure us that the inconvenience would not be comparable to that caused by laying a gas, water, or telephone system. When one of those has been laid the annoyance, they urge, has only begun. The streets must be periodically reopened for the purpose of making thousands of house connections, extensions, and repairs. When a pneumatic tube is once down it is good for a generation at least. It is not subject to recurrent alterations incidental to house connections and repairs. In three American cities the tubes have been touched but three times in twelve years, and in those cases the causes were a bursting water main and faulty adjacent electric installations. The repairs were effected in a few hours.
From a general consideration of the scheme we may now turn to some mechanical details. The pipes would be of 1 foot internal diameter, made in 12-foot lengths. "Straight sections," writes an engineering correspondent of The Times, "would be of cast-iron, bored, counter-bored, and turned to a slight taper at one end, to fit a recess at the other end (of the next tube), to form the joints, which could be caulked. Joints made in this way are estimated to permit of a deflection of 2 inches from the straight, so that the laying and bedding need not be exact. Bent sections are to be of seamless brass; these are bored true before bending. The permissible curvature is determined upon the basis of a maximum bend of 1 foot radius for every 1 inch of diameter; the 1 foot diameter of the London tubes would consequently be allowed a maximum curvature of 12 foot radius. Measured at the enlarged end, the over-all diameter of each pipe is 17 inches, and as two such pipes are to be laid side by side, with 18 inches between centres, the clear width will be 35 inches. The trenches are therefore to be cut 36 inches wide, and in order to have a comparatively free run for the sections, it is proposed to cut the trenches 6 feet deep."
When the hundred miles of piping have been laid, the entire system will be tested to a pressure of 25 lbs. to the square inch, or about two and a half times the working pressure. Engines of 10,000 h.p. will be required to feed the lines with air, for the propulsion of the carriers, each 3 feet 10 inches long, and weighing 70 lbs.
In order to ensure the delivery of a carrier at its proper destination, whether a terminus or an intermediate station, Mr. Batcheller has made a most ingenious provision. On the front of a carrier is fixed a metal plate of a certain diameter. At each station two electric wires project into the tube, and as soon as a plate of sufficient diameter to short-circuit these wires arrives, the current operates delivery mechanism, and the carrier is switched off into the station box. The despatcher, knowing the exact size of disc for each station, can therefore make certain that the carrier shall not go astray.
It may occur to the reader that, should a carrier accidentally stick anywhere in the tubes, it would be a matter of great difficulty to locate it. Evidently one could not feel for it with a long rod in half a mile of tubing—the distance between every two stations—with much hope of finding it. But science has evolved a simple, and at the same time quite reliable, method of coping with the problem. M. Bontemps is the inventor. He located troubles in the Paris tubes by firing a pistol, and exactly measuring the time which elapsed between the report and its echo. As the rate of sound travel is definitely known, instruments of great delicacy enable the necessary calculations to be made with great accuracy. When a breakdown occurred on the Philadelphia tube line, Mr. Batcheller employed this method with great success, for a street excavation, made on the strength of rough measurements with the timing apparatus, came within a few feet of the actual break in the pipe, caused by a subsidence, while the carriers themselves were found almost exactly at the point where the workmen had been told to begin digging.[23]
There is no doubt that, were such a system as that proposed established, an enormous amount of time would be saved to the community. "A letter from Charing Cross to Liverpool Street," says The World's Work, "occupies by post three hours; by tube transit it would occupy twenty to forty minutes, or by an express system of tube transit ten to fifteen minutes. Express messages carried by the Post Office in London last year (1903) numbered about a million and a half, but the cost sometimes seems very heavy. To send a special message by hand from Hampstead to Fleet Street, for example, costs 1s. 3d., and takes about an hour. It is claimed that it could be sent by pneumatic tube at a cost of 3d. in from fifteen to twenty minutes, and that for local service the tube would be far quicker than the telegraph, and many times cheaper."
It has been calculated that from one-sixth to one-quarter of the wheeled traffic of London is occupied with the distribution of mails and parcels; and if the tubes relieved the streets to this extent, this fact alone would be a strong argument in their favour. It is impossible to believe that tube transmission on a gigantic scale will not come. Hitherto its development has been hindered by mechanical difficulties. But these have been mostly removed. In the United States, where the adage "time is money" is lived up to in a manner scarcely known on this side of the Atlantic, the device has been welcomed for public libraries, warehouses, railway depôts, factories—in short, for all purposes where the employment of human messengers means delay and uncertainty. Twenty years ago Berlier proposed to connect London and Paris by tubes of a diameter equal to that of the pipes contemplated in the scheme now before Parliament. Our descendants may see the tubes laid; for when once a system of transportation has been proved efficient on a large scale its development soon assumes huge proportions. And even the present generation may witness the tubes of our big cities lengthen their octopus arms till town and town are in direct communication. After all it is merely a question of "Will it pay?" We have the means of uniting Edinburgh and London by tube as effectually as by telephone or telegraph. And since the general trend of modern commerce is to bring the article to the customer rather than to give the customer the trouble of going to select the article in situ—this applies, of course, to small portable things only—"shopping from a distance" will come into greater favour, and the pneumatic tube will be recognised as a valuable ally. We can imagine that Mrs. Robinson of, say, Reading, will be glad to be spared the fatigue of a journey to Regent Street when a short conversation over the telephone wires is sufficient to bring to her door, within an hour, a selection of silver ware from which to choose a wedding present. And her husband, whose car has perhaps broken a rod at Newbury, will be equally glad of the quick delivery of a duplicate part from the makers. These are only two possible instances, which do not claim to be typical or particularly striking. If you sit down and consider what an immense amount of time and expense could be saved to you in the course of a year by a "lightning despatch," you will soon come to the conclusion that the pneumatic tube has a great future before it.
FOOTNOTE:
[23.] Cassier's Magazine, xiii, 456.
[CHAPTER XXIII]
AN ELECTRIC POSTAL SYSTEM
Far swifter than the movements of air are those of the electric current, which travels many thousands of miles in a second of time.
Thirty miles an hour is the speed proposed for the pneumatic tube system mentioned in our last chapter. An Italian, Count Roberto Taeggi Piscicelli, has elaborated an electric post which, if realised, will make such a velocity as that seem very slow motion indeed.
Cable railways, for the transmission of minerals, are in very common use all over the world. At Hong-Kong and elsewhere they do good service for the transport of human beings. The car or truck is hauled along a stout steel cable, supported at intervals on strong poles of wood or metal, by an endless rope wound off and on to a steam-driven drum at one end of the line, or motion is imparted to it by a motor, which picks up current as it goes from the cable itself and other wires with which contact is made.
Count Piscicelli's electric post is an adaptation of the electric cableway to the needs of parcel and letter distribution.
At present the mail service between towns is entirely dependent on the railway for considerable distances, and on motors and horsed vehicles in cases where only a comparatively few miles intervene. London and Birmingham, to take an instance, are served by seven despatches each way every twenty-four hours. A letter sent from London in the morning would, under the most favourable conditions, not bring an answer the same day—at least, not during business hours. So that urgent correspondence must be conducted over either the telephone or the telegraph wires.
Count Piscicelli proposes a network of light cableways—four lines on a single set of supports—between the great towns of Britain. Each line—or rather track—consists of four wires, two above and two below, each pair on the same level. The upper pair form the run-way for the two main wheels of the carrier; the lower pair are for the trailing wheels. Three of the wires supply the three-phase current which drives the carrier; the fourth operates the automatic switches installed every three or four miles for transforming the high-tension 5,000-volt current into low-tension 500-volt current in the section just being entered.
The carriers would be suitable for letters, book-parcels, and light packages. The speed at which they would move—150 miles per hour to begin with—would render possible a ten-minute service between, say, the towns already mentioned. The inventor has hopes of increasing the speed to 250 m.p.h., a velocity which would appear visionary had we not already before us the fact that an electric car, weighing many tons, has already been sent over the Berlin-Zossen Railway at 131 1 / 2 miles per hour. At any rate, the electric post can reasonably be expected to outstrip the ordinary express train. "Should such speeds as Count Piscicelli confidently discusses," says The World's Work, "be attained, they would undoubtedly confer immense benefits upon the mercantile and agricultural community—upon the agricultural community because in this system is to be found that avenue of transmission to big centres of population of the products of la petite culture, in which Mr. Rider Haggard, for example, in his invaluable book on Rural England, sees help for the farmer and for all connected with the cultivation of the soil. Count Piscicelli proposes to obviate the delays at despatching and receiving towns by an inter-urban postal system, in which the principal offices of any city would be connected with the head-office and with the principal railway termini. From each of the sub-offices would radiate further lines, along which post-collecting pillars are erected, and over which lighter motors and collecting boxes (similar to the despatch boxes) travel. The letter is put in through a slot and the stamp cancelled by an automatic apparatus with the name of the district, number of the post, and time of posting. The letter then falls into a box at the foot of the column. On the approach of a collecting-box the letter slot would be closed, and by means of an electric motor the receptacle containing the letters lifted to the top of the column and its contents deposited in the collecting-box, which travels alone past other post-collecting poles, taking from each its toll, and so on to the district office. Here, in a mercantile centre, a first sorting takes place, local letters being retained for distribution by postmen, and other boxes carry their respective loads to the different railway termini, or central office."
Were such an order of things established, there would be a good excuse for the old country woman who sat watching the telegraph wire for the passage of a pair of boots she was sending to her son in far away "Lunnon"!
[CHAPTER XXIV]
AGRICULTURAL MACHINERY
PLOUGHS — DRILLS AND SEEDERS — REAPING MACHINES — THRESHING MACHINES — PETROL-DRIVEN FIELD MACHINERY— ELECTRICAL FARMING MACHINERY
Agriculture is at once the oldest and most important of all national industries. Man being a graminivorous animal—witness his molar, or grinding, "double" teeth—has, since the earliest times, been obliged to observe the seasons, planting his crops when the ground is moist, and reaping them when the weather is warm and dry. Apart from the nomad races of the deserts and steppes, who find their chief subsistence in the products of the date-palm and of their flocks and herds, all nations cultivate a large portion of the country which they inhabit. Ancient monuments, the oldest inscriptions and writings, bear witness to the prime importance of the plough and reaping-hook; and it may be reasonably assumed that the progress of civilisation is proved by the increased use of cereal foods, and better methods of garnering and preparing them.
For thousands of years the sickle, which Greek and Roman artists placed in the hand of their Goddess of the Harvest, and the rude plough, consisting of, perhaps, only a crooked bough with a pointed end, were practically the only implements known to the husbandman besides his spade and mattock. Where labour is abundant and each householder has time to cultivate the little plot which suffices for the maintenance of his own family, and while there is little inducement to take part in other than agricultural industries—tedious and time-wasting methods have held their own. But in highly civilised communities carrying on manufactures of all sorts it is difficult for the farmer to secure an abundance of human help, and yet it is recognised that a speedy preparation and sowing of the land, and a prompt gathering and threshing of the harvest, is all in favour of producing a successful and well-conditioned crop.
In England, eighty years ago, three men lived in the country for every one who lived in the town. Now the proportion has been reversed; and that not in the British Isles alone. The world does not mean to starve; but civilisation demands that as few people as possible should be devoted to procuring the "staff of life" for both man and beast.
We should reasonably expect, therefore, that the immense advance made in mechanical science during the last century should have left a deep mark on agricultural appliances. Such an expectation is more than justified; for are there not many among us who have seen the sickle and the flail at work where now the "self-binder" and threshing machine perform the same duties in a fraction of the time formerly required? The ploughman, plodding sturdily down the furrow behind his clever team, is indeed still a common sight; but in the tilling season do we not hear the snort of the steam-engine, as its steel rope tears a six-furrow plough through the mellow earth? When the harvest comes we realise even more clearly how largely machinery has supplanted man; while in the processes of separating the grain from its straw the human element plays an even smaller part. It would not be too much to say that, were we to revert next year to the practices of our grandfathers, we should starve in the year following.
This chapter will be confined to a consideration of machinery operated by horse, steam, or other power, which falls under four main headings,—ploughs, drills, reapers, and threshers.