THE LIGHTING OF LONDON
LONDON is lighted by gas, by petroleum, by candles, by electricity, and by a few odds and ends with which we need not at present concern ourselves. The chief work is done by gas, and the amount of that luminant consumed in the London area runs into large figures. The Metropolitan Gas Companies - officially so called are three in number; they are the Gas Light and Coke Company, the South Metropolitan Company, and the much smaller Commercial Company; but these only do the larger proportion of the work. Around their districts, and branching into them, are many minor companies whose output must be included in any estimate of the consumption. Taking all the companies together, we shall find that London takes over 29,000,000,000 cubic feet of gas per year, led through its streets in over 3,800 miles of mains. and obtained from over 2,850,000 tons of coal. If this coal was stacked in one place it would form a rectangular heap about as long and broad and high as St. Paul's Cathedral, including the lightning conductor on the cross. Let us remember this. It may serve us in good stead when we are considering how fast our misguided country is using up its stores of energy.
The lion's share of this great work is done by the Gas Light and Coke Company, who light over 60 square miles and own over 1,800 miles of main. They are an amalgamation of many companies, and their works are scattered all over London. They have storage stations at Agar Town, Bethnal Green, Battersea, Vauxhall, and Horseferry Road. They have the works of the old Imperial Company at Bromley, Shoreditch, Fulham, and St. Pancras; the old Great Central works at Bow; the Independent works at Haggerston; the Nine Elms works of the old London; the Pimlico works of the Equitable; and the Kensal Green works of the Western. But at Beckton, their largest station, as much gas is made as at all these works put together, and the Beckton gas will be found lighting the London lamps fifteen miles away from where it was made. From Beckton to Horseferry Road run two mains. These mains are each four feet in diameter. This is alone sufficient to show what Beckton can do.
Beckton is approached across a waste, shaggy flat, the Gas Company's "reserve," cut up into squares by black roads and sluggish drains, in which, curiously enough, flourishes the Michaelmas daisy. There is room enough and to spare. The works are the largest in the world, and extend over an area as large as Clapham Common. They are named after Mr. Simon Beck, who was governor of the Chartered Gas Company at the time of their projection. Then their site was a swamp, and it was necessary to go down forty feet to find a foundation; now there are no firmer buildings or busier colony on Galleons Reach. Standing out four hundred feet into the Thames is a jetty twenty-eight feet above high-water mark, and giving sufficient frontage for 12,000 tons of coal to be unloaded in the twenty-four hours by the aid of the steam and hydraulic machinery with which the 'tween decks is loaded. And the coal, as it is lifted aloft by the cranes, three to each collier, is shot into railway trucks, and run at high level into the works.
There is little mystery in the manufacture of gas. The coal is cooked in retorts, and every ton, there or thereabouts, gives off 10,000 cubic feet of gas, 12 sacks of coke, 10 gallons of tar, 14 gallons of ammoniacal liquor, and 1 cwt. of breeze. The furnaces are lighted and worked up to a white heat. In three days, perhaps, they will be ready. The retorts, long, circular, or D-shaped ovens of firebrick made up of a centre and ends and closed in by iron doors, are arranged on the benches in each furnace-arch in fives, or sevens, or nines, and from above each door rises a pipe to the hydraulic main. The feeding of the retorts with the proper mixture of ordinary coal and cannel is not an operation requiring a high grade of intelligence. A long scoop, like a cheese-taster, is laid on the stone floor and filled with " nubbly bits;" and the taster is thrust into the retort, turned over, and withdrawn. No wonder that human muscle is being replaced by gearing worked by compressed air. In this mechanical contrivance the coal is shot or elevated into a hopper; the hopper fills a feeding-trough that fits the retort; the retort-door is thrown open, the feeder is introduced, and its grooves opening, shed their contents into the fiery oven. Twice the feeder is thrust in from each end of the twenty-feet retort, and the coal is spread evenly all along. Then the doors are closed, and in four, five, or six hours, according to the temperature, the coal will have lost all that is worth taking from it. Then the door is opened, the coke drawn and run out, to be cooled at the bed and broken up, and come back to feed the furnace, so that the retort can be said to be heated by the coke it has previously made - not by all the coke, of course, for a good deal is sold to the public, and forms one of the profitable waste products. The Gas Light Company uses 1,880,000 tons of coal, and sells nearly 1,300,000 chaldrons of coke in a year.
At Beckton there are twelve retort-houses, the largest being 510 feet long and 100 feet wide, and having 45 beds each of nine retorls, making 405 in all. On each side are two lines of standard gauge railway, one over the other - the high-level for the incoming coal, the low-level for the outgoing coke. It is warm work in the retort-house; the half-naked stokers are as shiny as negroes and almost as black, for the perspiration clothes them with a skin-tight coat of moisture that lets no speck of dust pass by. And the labour is heavy - on the average a Beckton stoker deals with 4 tons 8 cwt. 22 lb. of coal per day.
The hydraulic main into which the ascending tubes from the retorts deliver is a huge pipe, half-full of slowly-running water, in which the gas is received and the tar and other products are condensed. It leads out to the pipe-condensers, and there the gas travels in a labyrinth until its temperature has been considerably reduced, and the naphthalin difficulty minimised. Along the labyrinth it is sucked by the exhauster, its pressure being regulated by governors at occasional intervals. And then it is cooled down and passes the exhauster, which is practically an air pump. Up to it the gas is sucked, from it onwards the gas is driven to undergo its purification. It is washed by being sent through the bubbling water that forms the ammoniacal liquor, of which the three metropolitan gas companies make eighty million gallons a year. It is scrubbed from the ammoniacal gases by being driven up towers filled with wet coke or honeycombed with thin deal boards or by some other contrivance. It is purified from sulphuretted hydrogen by being driven through" grids" of slaked lime, and sometimes it is passed through oxide of iron. And finally it goes through a meter as big as a railway carriage, and enters the gasholder. At Beckton the largest holders contain two millions of cubic feet; at the new East Greenwich works of the South :Metropolitan Company there is one holding eight million cubic feet, the largest in the world; at the Old Kent Road works of the same company there is one holding five and a half million cubic feet. This last is a familiar object to the South Londoner, and quite a famous holder in its way. It cost £47,000 , and i in three lifts of 208, 211, and 214 feet respectively, each ring being about 53 feet deep.
With it we may as well end our rapid survey, in which we have advisedly steered clear of tests and bypaths. From the holder the mains run into the road, but as the gas passes the gate of the works it has to undergo a final examination. It must go out at a certain pressure, and a battery of gauges and appliances are here to qualify it accordingly. It must be of a certain lighting standard, and so it feeds a light that is not only perennial, like the sacred lamps of old, but, unlike them, is in constant comparison with a photometer, that it may be kept up to the mark. It must contain no sulphuretted hydrogen, and to ensure this there are hung in its path two little slips of white acetate of lead paper, which would instantly turn black with anger at the approach of 0 obnoxious an intruder. We need follow gas no further; suffice it to say that the London bill amounts to rather over £4,000,000 a year.
Next in importance to gas as a luminant stands petroleum, the consumption of which has increased so enormously of late years. Close upon a hundred million gallons are now yearly imported into the United Kingdom, and to this should be added the unfortunately decreasing output of the Scotch companies. The wells of America and the springs of Baku have almost swamped the home industry, but they have made petroleum so cheap that it is becoming a dangerous rival to gas, not only as regards cheapness, but as regards power of light. Only a year ago Gravesend, having to choose between gas and oil for street-lighting, deliberately chose oil as being cheaper and giving a better light for the money. Even in the London area there are streets lighted by petroleum. And the recent improvements in the treatment of petroleum, in its gaseous as well as in it liquid state, show that we have not yet reached the limit of its excellence, and that for hydro-carbon there is, indeed, a good time coming. But on petroleum, as on the by-products of gas manufacture, we might fill pages, and that is not our immediate purpose here. Petroleum is used for many purposes now, that the amount consumed for lighting alone is not easily arrived at. Often 4,000,000 gallons at a time are stored at one pot in the metropolis, but what the metropolitan consumption is can only be guessed at. We shall be well within the mark in estimating it at 10,000,000 gallons.
As regards candles, we are in the same difficulty. No statistics exist which would enable us to apportion the London share. Over 36,000 tons of candles are made in the kingdom in a year, and an increasing number of candles are imported to be set against the amount of British exports, chiefly to the colonies. It has been estimated that the gas consumption is represented by a burner per head, and that the candle consumption has now dropped till it averages but a pound to every gallon of mineral oil. If this be correct, London would take over 4,000 tons, which seems to be rather too liberal an allowance. However, we may include in the amount the colza and other vegetable oils, and so put ourselves on the right side.
The minor luminants we can afford to disregard. Practically, oil is the light of the poor, and gas the light of the well-to-do; but that gas will eventually have to give electricity a large share in its lighting dominion is inevitable.
The electric light has passed through all the stages needful for success in these days. It has run the gauntlet of over-advertising, patent-evading, and shareholder-plucking, and, apparently subsiding overwhelmed, has risen with new vigour and begun its business career on a foundation of ruined reputations in that quiet, steadily-growing way distinctive of a solid industry. With the late Board of Trade inquiry it entered on a new stage. The report of Major Marindin marks an epoch in the lighting of London.
The inquiry was held, it will be remembered, under the Electric Lighting Acts of 1882 and 1888 with reference to the applications of some thirteen companies for provisional orders and licences to supply electricity - or "energy," as it is thought best to call it - in different districts of the metropolis. The report is worth reading. In it "Recommendations" it allotted to the London Electric Supply Association all that part of St. Martin's-in-the-Fields lying south of the Strand and west of St. Martin's Lane, all Westminster north of Victoria Street, except the small portion west of St. George's Hanover Square; all St. James's, and all St. George's Hanover Square, and Chelsea; and on the south of the Thames, Greenwich, Rotherhithe, Bermondsey, Southwark, and that part of Lambeth north of Westminster Bridge Road. To the Metropolitan Electric Supply Company were allotted St. Giles's, St. George's Bloomsbury, Holborn, St. Sepulchre's, Hatton Garden, Soho, Covent Garden, the Savoy, St. Mary-le-Strand, St. Marylebone, St. Mary Lambeth, Clapham, and Streatham; and to the same company was allotted that part of St. Martin's-in- the-Fields east of Northumberland Avenue, Charing Cross, and St. Martin's Lane. By this arrangement the only area in which there will be two competing alternating current companies is in North Lambeth, where such a state of affairs could not well be avoided owing to the outlying southerly territory claimed by the Metropolitan. Kensington and Knightsbridge were shared among the House-to-House Electric Light Supply Company, the Kensington and Knightsbridge Electric Lighting Company, the Notting Hill Electric Lighting Company, and the Chelsea Electricity Supply Company. To the Westminster Electric Supply Corporation was given a share in Westminster. For Paddington and St. Pancras there was no grant recommended, as those parishes had expressed their intention of carrying out their electric lighting for themselves. Since the report the City authorities have divided up their important territory, and given the western third to the Metropolitan Company, the centre to the Anglo-Brush Company, and the east to the London Electric Supply, under which three contracts 395 arc lamps are to take the place in the thoroughfares of 1,730 gas-lamps, and give more than double the light at less than double the cost. And there have been other advances; among them Clerkenwell and Newington have been assigned to the London. Many of these allotments have been begun upon, and there are very few that will not be taken up. In the coming year there are 115 applications for lighting in the metropolitan area. Of these the London is responsible for 41, the Metropolitan for 6, and the House-to-House for zo, mostly for the outlying districts. One sign of the times is noteworthy. Among the 479 applications for the whole country, three are from gas companies, who propose to combine the old and new lights, and supply their customers with either.
By far the largest of the companies is the London Electric Supply Corporation, to which the main share in lighting the metropolis has been assigned. Their central station at Deptford is not only the largest in the country, but it is - and for some time will probably continue to be - the largest in the world. On the Continent every capital has its light-station, and there is hardly a town in the United States which has not its installation; but nothing on so large a scale as the Deptford works has as yet been thought of out of Britain.
Five years ago Sir Coutts Lindsay made up his mind to light the Grosvenor Gallery by electricity. "Put down twice the machinery, produce twice the current you require, and let me have what you can spare." So said a neighbour. Other neighbours joined in, and the installation began to grow. The Earl of Crawford and Lord Wantage joined Sir Coutts, and the private company familiarly known as the Grosvenor Gallery Company was formed. Still the demand grew, and" Sir Coutts Lindsay and Co., Limited," developed into the London Electric Supply Corporation, working from the Grosvenor no less than 33,000 lamps, and lighting an area extending from Regent's Park to the Thames, and from Knightsbridge to the Corporation Griffin. Now the Grosvenor is to become a mere subsidiary station, and the main work is to be done at Deptford, and extend over a radius of thirteen miles.
The two systems, the old and the new, are thus brought into keen contrast on London's great highway. Approaching the City by the river, Beckton, with its two hundred acres, lies to the right; Deptford, with its four acres, to the left. Beckton takes its 30,000 tons of coal a week; Deptford, in full swing, will take but 3,000; and while Beckton is supplying its half million of lights, Deptford will supply just double as many.
The Deptford engine-house, as it at present stands, is a wonder. It is a hundred feet high from the floor to the roof, 195 feet long, and two cricket pitches across. The boiler-house on the other side of the wall is 70 feet broad, and contains boilers now giving steam for engines of 13,000 horse-power; these are the first instalment of a series which will soon be ready to give 65,000 horse-power, and then be duplicated. These boilers are on two floors, the upper floor being supported on pillars 30 feet high; and above this upper floor is another floor similarly supported on 30-feet pillars, which will contain the store of coal which will be supplied to the furnaces by means of vertical shoots running through the centres of the floors of the upper boilers to the lower ones. From this lofty coal-yard, a high-level railway will run out on to the wharf, so that the steam colliers will be unloaded direct into the trucks, and the trucks run at once to shoot their contents on to the top storey.
Each battery of six boilers is placed in connection with four sets of "economisers;" the steam from the boilers is gathered in steam-drums above the ordinary water-drums, and the steam-pipes leading to the engines are in duplicate. At each end of the boiler-room is a chimney-shaft-not a tall, slender cylinder, but a massive square tower 130 feet high, pierced by four flues. Besides the high-level line, there is a low-level railroad, starting from the river and running through the middle of the buildings, and at right-angles to this, 50 feet and more overhead, run two travelling cranes, one lifting 50 tons, the other 25 tons.
The engine-room is divided into halves by a row of tall columns supporting the roof and these cranes. In the half near the river are two dynamos, each driven by a 1,500 horse-power engine. In the half away from the river are to be two large dynamos, each driven by a 10,000 horse-power engine. What the large dynamos will look like when set up can be seen from a dividing-engine on the floor, on which the semi-circumference of one of the armatures is being spaced out. The circle is 46 feet across - the biggest thing ever projected in electric engineering, and a sort of Laxey wheel among dynamos. The engines and dynamos are combined in such a manner that this 46-feet armature will be driven direct, and act as a flywheel. The crank-shafts, of which three were cast at Beardmore's, are the largest castings ever made in Scotland. They are over 36 feet long and a yard in diameter, and each in the rough weighs 75 tons. When these great engines are going at full power they will each supply current for 200,000 lights. And all further engines are to be of this size. Up to a certain limit, there is no doubt that the larger the generator the more economically it can be worked. Whether the limit has been exceeded in these giant machines remains to be discovered.
Even the small dynamos in the north-western corner, driven by the 1,500 horse-power engines, are the largest electrical generators yet built. They each supply 25,000 lights; the Grosvenor Gallery dynamos, which have hitherto held pride of place as yielding the highest electrical efficiency, supply-ing only 15,000 lights. The armatures are 14 feet 6 inches in diameter, and are mounted direct over one end of the driving-pulleys, which are 7 feet 6 inches in diameter and 8 feet wide. The machines are of the Ferranti type - Mr. Ferranti is the company's engineer and the designer of these Deptford works - and the copper-ribboned armatures are as usual thin, so that the magnet-poles are very close and the field of force intense. One safety appliance is remarkable - the brushes are in a box magnetically locked, so that as long as the current is passing they cannot be got at. Between these dynamos and the wall are three "exciters" of the Kapp pattern, and on the other side of the central railway is a space reserved for condensing-engines, but temporarily occupied by steam tools, among them the largest planing-machine yet made, taking 20 feet horizontal and 20 feet vertical. When the engine-room is complete it will contain a special winding-engine and barring-engine, by the aid of which the 46-feet dynamos will be taken to pieces in a minute and a half. In the small engines now erected, the facilities for slipping them apart are distinguishing features; the heavier pieces rest on sliding-beds, and are held in position by a few powerful screws, which can be loosened in an instant, and drop down into grooves, so as to clear the slide at once.
The hall has been designed and the machinery placed so that from an elevated gallery the engineer will have the whole in view at all times - and a wonderful sight it will be. No wonder that "the making of the lightning " on such a scale has caused the timid to fear that the "attraction" may be rather in excess at Deptford, and that the "influence" may be over-strong. Such an amount of power will never before have been gathered on so small an area - never, that is, since Laurie's Norbert went flying moonwards with the Peak of Tehbali.
And all from the spinning of a wheel! Fifty-eight years ago Faraday discovered electro-magnetic induction; that currents could be induced in a closed circuit either by moving magnets near it, or by moving the circuit across the field, or by a current with changing strength. His discovery suggested the magneto-electric machine, Pixii's being the first, in 1833. Two-and-twenty years ago Siemens and Wheatstone independently found that a coil rotating between the poles of an electromagnet would, from the feeble residual magnetism, induce a small current, which, when transmitted through the coils of the electro-magnet, might exalt its magnetism, and so prepare it to induce still stronger currents; and from this discovery came the dynamo of which in the colossal Ferrantis we have the latest and largest development.
And now, having got this tremendous current, how is it distributed? The trunk main is made at Deptford. It is in 20-feet lengths and is 2 7/8 of an inch in diameter. First, a copper tube is taken, and in a lathe-like apparatus which is fitted with a long trough, it is covered with the insulating material and taped in spirals; then the insulated tube is thrust into a larger copper tube and the long bar is drawn as if it were wire, so that the copper case and the insulating material are pressed hard and compact on to the conducting tube; then the outer tube is coated with another eighth of an inch of insulator, and this in its turn is pressed into a steel pipe to protect the whole from injury. This is quite a new form of cable, the object of the change being to cut off all risk of danger. If anything were to go wrong with the conductor, the insulating material would simply be burnt through, and by means of the casing connection would immediately and harmlessly be made with the ground. These solid 20-feet lengths are joined by a conical joint and form a continuous bar, and this bar, "the trunk main," comes to London along the railways. By arrangement with the South-Eastern, the Chatham and Dover, the Brighton and South Coast, and the District Companies, the main is brought to the terminal railway stations, and run along the Inner Circle line to different points in the London area. This co-operation of the railways is the great feature of the London supply scheme. The current leaves Deptford at the unprecedentedly high pressure of 10,000 volts; at transforming stations, such as Ludgate and Charing Cross, it is "expanded" to 2,500 volts, and taken in distributing mains to the consumers' premises; there it is again "expanded," and at a pressure of 100 volts or 50 volts it enters the house and lights the lamps. The" transformers" are on the principle of induction coils; the primary coil, consisting of many folds of thin copper, receives the incoming small currents of high potential; the secondary, consisting of fewer folds of thicker copper, delivers the enlarged currents at a lower potential, the "watts" of the secondary being equal in number to the "watts " of the primary, while the" volts" of the secondary are to the volts of the primary as are the number of the folds in the two coils.
"Volts and watts indeed!" says the wondering reader, "and what are they? Give me a definition!" A reasonable request, surely; for was there not a time when even cubic feet and atmospheres had to be defined in the terms of some other mode of measurement? And volts and ohms and amperes and watts will soon be as familiar to the London housewife as pecks and pounds and feet and gallons. The volt is the practical unit for the measurement of electro-motive force, and without going into detail may be taken as representing a little less than the amount of that force given by one Daniell's cell. The ohm is the practical unit of resistance. The ampere is the unit of current obtained by the potential of one volt through one ohm. The watt is the unit of electric power; it is the amount given by one ampere working through one volt; and it may be as well to note that there are 746 watts in one horse power.
But enough of the London scheme. The system adopted by the Metropolitan and House-to-House Companies is the supply from a number of generating stations, in or near to the area lighted, by distributing mains carrying the current at a pressure of from 2,000 to 1,000 volts to the consumers' premises, or to distributing stations, where, as in the London system, it will be transformed to a pressure of 100 or 50 volts. Thus, the three chief companies are agreed in supplying high-pressure alternating currents and transformers.
But at present it has not been found practicable to utilise alternating currents for the purposes of driving power - to work a motor a continuous current is required. Such a current is given by the Chelsea Company, who have one generating station for a considerable area, and charge with a pressure of from 1,000 to 2,000 volts several accumulator stations, there being duplicate sets of batteries at different points within the lighting area. From these stations the current is carried direct into the consumers' premises at a pressure of 100 volts, the supply being quite free from accumulators. A continuous current is also supplied by the Kensington and Knightsbridge Company, who work partly by accumulators and partly by dynamos, the former doing the whole task during the hours of minimum supply, and the latter being employed in charging the batteries and supplementing the direct supply from them during the hours of maximum requirement. It is this system which the Notting Hill Company and Westminster Company propose to adopt. The system of the St. James's and Pall Mall Company, whose D-shaped trays and copper band conductors have recently made themselves so conspicuous in traffic obstruction at the West-end, is the simple direct one at low pressure, without any accumulators, and available only over small radii so as to necessitate a large number of generators.
Which of these systems is to triumph in the long run time will show. At present the policy of the Board of Trade is to allow not more than two companies in the same area, one of these to supply alternating currents, the other continuous; to make them lay their mains in the same subways or conduits; and leave the fittest in the struggle to survive.
W. J. GORDON.
Leisure Hour, 1889