practically arriving at the amount of the inculpated impurities in industrial laboratories. The investigations of Mr. Braune give an unforeseen prominence to this industrial problem of paramount importance, and point to the nitrogen as the agent, which no one has hitherto suspected. This new enemy of metals, which is

indicated as the cause of the anomalies to which reference has been made, can readily be estimated by analysis, and it will thus shortly be possible to define very precisely the sphere of its action, and probably to overcome it without any great difficulty. These researches have the advantage of co-ordinating a whole series of scattered facts, for which no explanation has hitherto been found. Certain of these are alluded to by the Author, and are considered in this new light. Mr. Braune has, moreover, shown that the nitrogen of the atmosphere cannot act directly on the iron, but that the intervention of basic slags is needful in a reducing medium; the fixation thereof is in direct relation to the formation of cyanides, and, as it was already well known that blast furnaces producing cyanide of potassium yield a bad quality of iron, Mr. Braune was led by this fact to inquire into the action of the nitrogen. It will be seen that a wide field of study of a novel character has been opened up by the discovery of Mr. Braune.

G. R. R.

Shipbuilding Cableway.

(The Engineer, London, 19 January, 1906, pp. 68-70.)

An ingenious application of the cableway to the building of ships has been in operation for some time in the yard of Palmers' Shipbuilding Company at Jarrow-on-Tyne. Roughly speaking, the installation consists of three lines of cables attached at either end to carriages working on a horizontal cross-girder. Each cross-girder is fixed on the top of two inclined columns, 100 feet apart and 125 feet long, which are themselves mounted on hinged pins, situated at ground level on massive concrete foundations arranged parallel to the crossgirders. The inclination of the columns is away from the cables in each case, so that the weight of the cross-girders and supports always tends to keep the cables taut. To prevent the cross-girders with their supporting columns falling outwards, two cables connect the corresponding ends of the two cross-girders, and each end of the latter is anchored to the ground by a further cable. The cableway has a clear span of 505 feet and commands 100 feet in width. The cable ends being secured to motor-driven carriages running on rails carried by the cross-girders, it is possible by moving the carriages relatively to the latter to adjust the position of each cable, as may be convenient, across the breadth of the space commanded by the cableway. The motors are reversible and transmit power through worm and tooth gear to a set of propelling wheels with their axis vertical, which are kept tightly pressed against the

top and bottom members of the cross-girder by the tension of the cable. The hoisting, lowering and longitudinal travelling and cross traversing motions of each cableway are all under the complete control of one operator who travels in the cage of the load-carriage. The longitudinal travelling can take place at a speed of 600 feet a minute, and lifting at 150 feet per minute.

A. W. B.

Raising of Wrecks. H. PIERRon.

(Revue Technique, Paris, vol. xxvi., pp. 446-8.)

The recent naval battles have shown how necessary it is to have efficient salvage appliances at hand, but the most perfect plant is still in possession of private companies, who have realized that appliances such as lifting chains are of little service in raising the large class of vessel now in use. One of the steamers recently constructed for salvage purposes is described and contrasted with the small class of vessel which is to be found in the various naval ports of France. This steamer has a length of 70 metres (229.6 feet) and a draught of 4 metres (13.1 feet), the horse-power being 1,500. The pumping appliances include one fixed centrifugal pump, capable of discharging 3,000 cubic metres per hour (11,000 gallons per minute); two movable centrifugal pumps, steam-driven, capable of discharging 1,200 metres per hour (4,400 gallons per minute); two similar pumps electrically driven, and one plunger pump. The whole of the movable pumps are kept on deck, so that they can be more expeditiously transferred to the wreck. The suction inlet for each of the movable pumps is provided with a chamber, from which branch six to ten inlets, any one of which can be used. The priming in all cases is effected by steam-ejectors, and is made the easier in that a branch from the suction-chamber can always be placed in the

sea.

All suction-branches are of rubber, with canvas insertion, and for each vessel they have a uniform diameter so as to be interchangeable. The length of flexible suction-pipe supplied is 800 metres (2,625 feet). The air required by the divers is compressed mechanically, the old-fashioned hand-pump being dispensed with. The article closes with a description of the raising of the French steamer "Chili," which sank at Bordeaux and lay embedded in the mud with a heavy list to port, the lower side of the deck being submerged even at low tide. An attempt, extending over three weeks, was made to float the vessel by means of barrels, but this proved unsuccessful, and the work was thereupon taken over by a Swedish salvage company, under the direction of which all openings were closed and the vessel was pumped out. Three weeks after this system was adopted the wreck was placed in graving dock. It is pointed out that the best salvage plant is owned in Sweden or Denmark, that Germany is not far behind, but that the appliances in England, and more especially in France, are totally inadequate for very heavy work.

I. C. B.

New Naval Coaling Station at Narragansett Bay, U.S.A.

(Engineering Record, New York, 25 November, 1905, pp. 599–603.)

The storage provides for about 54,000 tons, and there are some unusual features in it and in the loading plant. The stores are of two sheds, each 725 feet by 87 feet 6 inches, and are parallel with the coast line. The roofs have a slope corresponding to that of the natural inclination of the coal, the floor being of the same shape 15 feet below and parallel to it. Between these the coal is stored, and is let down by six rows of spouts of sheet steel 2 feet square, with double valve gates of a special design, to narrow-gauge trucks on six parallel roads leading to the pier. The roof principals are of inclined lattice girders, unsupported except at sides and at centre, along which latter a narrow-gauge track runs, for the delivery of the coal to the store. The inclined floor, which is of steel and reinforced concrete covered with a granolithic coating, is supported between the tracks by steel columns, protected by concrete against fire. Temperature tubes are distributed throughout the bin floors, so that, if incipient heating should occur, the fact will be announced immediately at the office. These tubes, which are fully described, contain thermostats which are set to close their circuits at an external temperature of 150° F., and by a system which is detailed not only the existence but the locality of the trouble is ascertained. There is an interesting description of the reinforced concrete of the floor, and of the side walls. The pier runs out at right angles to one end of the store, the other end being left for extension, and is of embankment for 200 feet, and steel for 300 feet, with three lines of narrowgauge track communicating with floor tracks of shed and the wharf beyond, and one standard-gauge line connecting the wharf and the New York, New Hampshire and Hudson River Railroad. Above, on an incline supported by columns, are the two narrow-gauge tracks leading from the wharf to the ridges of the stores, to supply the latter from the barges.

The wharf is a steel structure 400 feet long by 55 feet wide, running south and, being parallel to the shore opposite store sheds, forms with the pier an L-shape. It is surmounted by a full-length steel viaduct, carrying four level narrow-gauge tracks, and the 40-foot gauge track of the two travelling towers, full details of which are supplied, as well as of the loading arms 64 feet 9 inches and 79 feet 9 inches long, east and west respectively. These overhang on the land and sea side of the wharf, the former being for the colliers, and the latter for the battleships. The works were designed and carried out by Mr. Augustus Smith, of New York, and the coal-handling machinery and hoisting engines in the tower were built by the Mead-Morrison Manufacturing Company, of New York.

C. O. B.

Baden Reservoir of the St. Louis Waterworks.

(Engineering Record, New York, 21 October, 1905, p. 454.)

1

The 25-million-gallon reservoir now being completed at the Baden pumping-station of the St. Louis waterworks is chiefly remarkable for its walls, which are of reinforced concrete. They are of a section first employed by Mr. A. O. Cunningham, Chief Engineer of the Wabash Railroad, for bridge abutments at Monticello, Illinois, and in other bridges. The reservoir wall is 24 feet high from the base of the footing to the top of the coping. The footing is 15 feet wide and 18 inches thick, and the coping 39 inches wide and 1 foot thick, the wall proper being 1 foot thick at the top, and 2 feet 6 inches where it begins to widen out close to the bottom. There are buttresses 15 feet 9 inches apart, centre to centre, and 2 feet thick, with a considerable batter, viz., to 7 feet from the widened base of the wall. The reinforcement is shown with much detail in the illustrations accompanying the article, but may be generally described as being of gridiron form, the 6,000 cubic yards of concrete composing the walls being interpenetrated with about 500,000 lbs. of steel bars. Close to the face of the wall, horizontally, are eighteen 3-inch corrugated bars 10 inches apart, and twenty close to the back, these, also, extending through the buttresses vertically; there are fifteen 9-inch bars between centres of buttresses at the face of the wall, these being repeated near the sloping surface of the buttress. The wide footing is also similarly interlaced. The walls are backed with 18 inches of puddle. The floor consists of 9 inches of concrete on 18 inches of puddle, the former being laid in blocks with -inch joints filled with asphaltic cement, and suitable arrangements are made to drain the reservoir dry. The work is expected to be finished this year.

C. O. B.

System for Flushing the New Sewers of Mexico City.

ROBERT GAYOL, M. Am. Soc. C.E.

(Proceedings of the American Society of Civil Engineers, August, 1905, pp. 394-414.)

The sewers existing in the City of Mexico previous to 1885 had been commenced in the middle of the eighteenth century, and had been constructed without any plan or order. They were rectangular in form, of inadequate cross-section, and without any established grade, being built either of inferior brick or stone, in common mortar which had been dissolved out of the joints. They emptied into a canal, the putrid waters of which flowed past the houses in the east part of the city into Lake Texcoco, and as there was no outlet from the valley in which the city was built, the level of the lake was only reduced

1 See Engineering Record, 5 November 1904.

by evaporation. This resulted in the city being flooded after heavy rains, which left a coating of loathsome mud after the flood-waters had evaporated. It was therefore imperative, in order to get rid of the sewerage and to avoid inundations, to complete the drainage of the valley, which work had been commenced 300 years before, but not finished. To avoid the risk of extensive inundations, before the drainage of the valley was completed, four large centrifugal pumps were erected to keep down the water-level of the lake. The combined system of sewerage was adopted, and, as it often happens that there is no rain for a period of 7 months, a perfect system of flushing was provided. The city was divided into five zones, and along the centre of each a main sewer of large dimensions was constructed, which receives the discharge from the lateral sewers in that zone. To flush the sewers, water is led from the National Canal to the flushing pumps, which force the water into the distribution pipes with an initial head of 40 feet. The main distribution pipe has a diameter of 42 inches, and, starting from the pumping-station, it crosses the city from south to north. Nine branches are led off from it-five to the east and four to the west. At every street corner, where the distribution pipes pass, two 6-inch cast-iron branch-pipes are led to the starting-points of two lateral sewers; the flushing water enters them with an initial velocity of about 30 feet per second, which is soon reduced by friction to 5 feet or 6 feet per second-a velocity, however, which is sufficient to clean the sewer perfectly. In some cases it is necessary, in order to avoid complications, for a lateral sewer to receive its flushing water from another sewer, instead of from the distribution pipes.

The sewers are flushed every day, each valve remaining open, as a rule, about 15 minutes. Besides the flushing, a heavy mop is passed through each sewer, to remove from the walls grease and other substances which may adhere to them. The mop is drawn through the sewers between two manholes by means of a rope and a winch placed over the second manhole, a certain quantity of water being introduced when the mop is used, to carry off the substances loosened from the walls.

A. W. B.

Construction Details of a Modern Gas-Holder.

(Engineering News, New York, 26 October, 1905, pp. 421-3.)

This structure is one of six recently built in New York City. It consists of a cylindrical steel tank 195 feet in diameter and 39 feet 3 inches deep, with a steel-plate bottom, resting on a foundation of 4,100 piles, capped with 12-inch 12-inch timber balks covered by half timbers. On this platform was built a brick wall, 5 feet 6 inches thick and 8 feet deep, having an outside diameter of 199 feet; the space within this wall was filled to within 18 inches of the top of the wall with gravel washed and