T

fifty years

to

HE Nile has been very much in evidence lately, but we have heard a great deal about irrigation and very little about navigation. Mr. William Preece has brought his experience of bear upon this important aspect of the Nile question, and his conclusions were stated in the course of a valuable paper contributed last week to the Society of Arts. Sir William dealt principally with the question of the navigation of the Nile from Assouan to the sea, that is, the regulation of its currents, depth of water, channels, and banks, so that the motion of its boats shall be possible in all times and seasons both up and down stream. The Nile, he says, is virtually embanked from Assouan to the sea. It is practically a canal, and should be treated as a canal. The following paragraphs briefly summarise his views:

The chief point for careful consideration appears to me to be not only the control of the water, but the control of the silt. Thirty thousand tons of valuable mud are lost in the sea every year, and the rise of the bed of the river in the Delta is a very serious question. Navigation is thus checked, but the remedy is at hand. The outlets are to be cleared by dredging. More sediment will be utilised on the land. Currents will be regulated by storage and barrage. Floods will be under better management. But what is most urgently needed is the protection of the banks, the training of the river, its maintenance in well defined limits, a depth navigable in all seasons, and a call on Nature to assist man to regulate this precious water communication for his daily service.

The principal problem to be solved is how to secure that the Nile shall maintain its own current at a greater velocity than that which causes settlement and so maintain the depth of the river, and how to prevent the increase of this velocity so as to save the erosion of the banks. The Assouan dam has shown how to do it, and the Wadi Rayan appears to be an eligible depression to enable a second reservoir of the same storage capacity to be installed. It is a matter

under discussion, and serious objections, geological and financial, have been urged against its adoption: but let us hope that these objections will disappear under careful scrutiny and survey, for no more eligible position could possibly be secured for such a desirable scheme to supplement the Assouan reservoir, for it would reduce the evaporation difficulty to a minimum.

The works which Sir William considers necessary to improve the navigation of the Nile are thus detailed:

1. The removal of obstructive banks and shoals. It has been found in the Severn that the removal of shoals (submerged banks) and deepening the bed of the river by dredging has led to a marked increase in the flood discharging power of the river. The navigation has also been greatly improved.

2. The river banks in certain places where they are subject to erosion want to be well pitched to prevent this erosion, and to maintain the proper direction of the current. An admirable system of pitching is to be seen near the landing stage as Asyüt.

3. Quays want to be built at all towns where commerce is active, goods are landed, and passengers embark and disembark.

4. Shadüfs and Sakias require to be abolished, especially the former.

5. Training walls are needed to direct currents in useful directions. The following conclusion was adopted by the Seventh International Congress of Navigation at Washington in 1898 :—

The increase of depth effected by dredging, combined with the rectification of the banks, may, under certain circumstances in the condition of the régime of a river, furnish a satisfactory solution, as shown by the results obtained upon the Severn in England."

6. New lands want to be developed by the deposit of the silt and by the dredging of the river on reclaimed banks and places.

A word as to ways and means:

The number of boats of all classes plying exceed 22,000. The owners of 22,000 boats would surely submit to a small taxation of £1 per boat per annum to secure better information than they have now, and some attempt at buoying, marking, and beaconing channels.

IN

N a former article we described the new power station at Lot's Road, then in an early stage of construction. By the courtesy of the British Westinghouse Company we are now able to present our readers with views of the completed station, and equipment. It is destined to supply energy for working the whole District Railway system, and also the Baker Street and Waterloo, the Great Northern and Brompton, the Charing Cross and Hampstead, and the Edgware and Hampstead lines. These, in total, amount to over sixty-three miles of track, of which the District Railway supplies about forty, and will unitedly represent by far the heaviest and densest traffic of any electric line. The now practically completed power house contains 60,000 h.p. of generating machinery, covers over 3 acres of land, including yards, etc., and has cost some two and a half millions of money. The site upon which it stands measures

on the water frontage 1,100 ft., and on the Lot's Road side 824 ft.

The size of the building and the plant that it contains have involved the greatest care in laying the foundations, which consist of about 220 concrete piers sunk through strata of made ground, gravel, and sand, to the London clay at a depth of 35 ft.

At the eastern extremity of the site a large barge basin is situated, the function of which is to dock the barges conveying coal or other material to the works. Behind this is the oil cooling plant, and on the western extremity of the site a large bin for containing the furnace ashes before shipment. In the construction of the buildings little less than 20,000 tons of steel have been used, of which some 6,000 tons have gone to the main framework.

The chimneys, of which there are four, are built on the Custodis principle, with an internal diameter at the base of 19 ft., and a height of 275 ft., and are placed symmetrically, in pairs, in the boiler-house section, about a quarter of the length of the building from the ends.

The internal arrangements of the building, which

measures 453 ft. long by 175 ft. broad and 140 ft. high, are shown in cross-section, fig. 5, The coal bunkers are situated on the top floor, the capacity of which is 15,000 tons. As the boilers will consume some 800 tons of fuel daily when the station is in full working order, it is obvious that such a capacity is necessary. The coal is picked up from the barges by two one-ton grabtravelling cranes, and after being weighed is carried by belt and inclined conveyors to the top of the building. Here it is deposited upon another belt conveyor, which is so arranged as to effect its distribution to the several bunkers in any desired quantity. As an alternative to water borne coal, arrangements have been made to obtain the supply of fuel from sidings of the West London Extension Railway by further arrangements that bring the coal in at the opposite end of the bunkers.

The ashes from the fires are dealt with by selfdumping buckets running on rails laid under the ash hoppers on the ground floor. A storage battery loco motive hauls these to the barges, where they are unloaded by pneumatic hoists. Compressed air is used for sundry purposes, including the operation of the barge basin gate machinery, capstans, and sundry large valves in the power-house.

The boiler-house contains sixty-four Babcock and Wilcox water-tube boilers supported directly on the steel framework of the building, and space is left for the installation of sixteen more. Each possesses 5,212 square feet of heating surface, and is provided with a superheater of 672 square feet area. They are divided up into sets of eight, the number required to operate each turbine unit at full load. There is no steam connection between the various groups, except in one case, where a header for supplying steam to the auxiliaries is fed from two of them. Chain grate stoking gear is provided, with 83 square feet of surface for each boiler. Economisers with 10 ft. tubes are grouped behind the boilers with a by-pass flue, and the total pipe area installed allows 1,540 square feet of feed water heating surface per boiler.

The main steam piping runs down the boiler-house

side of the dividing wall and under the engine-room floor to the turbines, and is supplied with the usual valves and water pockets.

In the engine-room are installed eight Westinghouse steam turbine generating sets, each consisting of a turbine of some 7,300 b.h.p., coupled direct to a threephase alternator of 5,500 kilowatts capacity. The former are of the Westinghouse single cylinder, double flow type, and are designed to run with a steam pressure of 165 lb. per square inch, a superheat of 100 deg. F., and at a speed of 1 000 revolutions per minute. They are capable of sustaining an overload of 50 per cent. by aid of automatic by-passes, and are extremely economical in steam consumption.

The three-phase Westinghouse

The

alternators are of the revolving field type and on a non-inductive load will supply a current of 289 amperes per phase at a pressure of 11,000 volts. They are of 5,500 kilowatts capacity, with a frequency of 333 per second. revolving field is a solid forging of Whitworth fluidpressed steel, of good permeability, and is wound in the usual manner. The armature core of laminated iron is supported by a heavy cast-iron frame, divided horizontally, and is wound in slots

surface.

on

its inner

The four exciter units consist of an Allen-BritishThomson-Houston combinationf and have a capacity of 125 kilowatts at 125 volts when running at 375 revolutions per minute.

The condensers are on the dry vacuum principle, with separate motor-driven air and water pumps. They are installed in pits between the two rows of turbines and have each 15 000 square feet of cooling surface which is fed with circulating water, conveyed through 66-in. pipes from the Thames. The cooling system is based on the principle of the syphon and the 20 in. centrifugal pumps have simply to overcome the friction in these pipes. The condensing equipment was supplied by Messrs. J. H. Simpson and Co.

The switch gear is arranged on three galleries placed principally across the north side of the engine-room. It was supplied by the British Thomson-Houston Company and all the high tension switches are motor-operated by means of a low-pressure circuit controlled from a small pilot switchboard.

The main were supplied by the British Insulated and Helsby Cables, Ltd., and are laid in Doulton stoneware ducts. There are twenty-four substations on the line to each of which a duplicate feeder is run; sixty-four ducts have therefore been laid, which allow for some extension. The feeders are carried through the streets to the Earl's Court station of the District Railway, which is the nearest point to Lot's Road.

The substations of the Metropolitan District Railway supply direct current to the southern half of the Inner Circle, and to a very wide area extending from East Ham to Hounslow and from Sudbury to Wimbledon and Richmond. These points form approximately the bounds of the Company, and are all primarily supplied with power from Lot's Road.

The contract for the whole of the District Railway substations was awarded to the British Westinghouse Company, who are responsible for the design, manufacture and installation of all the buildings and plant.

The British Association.

The South African meeting of the British Association opens on August 15th, the President-elect being Professor G. H. Darwin, F.R.S. Among the presidentselect of the various sections are: Mathematical and Physical Science: Professor A. R. Forsyth, M.A., Sc.D., F.R.S.; Chemistry: T. Beilby; Geology: Professor H. A. Miers, M.A., D.Sc., F.R.S.; Engineering: Colonel Sir Colin Scott-Moncrieff, G.C.S.L., K.C.M.G., R.E. Lectures have been already arranged by Professor Arnold, on Compounds of Steel"; Professor Ayrton, on "Distribution of Power"; Professor Porter, on Mining"; Mr. G. W. Lamplugh, on "The Geology of the Victoria Falls"; and Sir William Crookes, on Diamonds."

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FIG. 5. LOT'S ROAD POWER STATION-CROSS SECTION.