remains in force till 1900, and by tacit agree ment from that date on until it is revoked by a twelve months' notice from either party. Its benefits and obligations are extended to all British possessions except Canada, Australia, and the south African colonies.

Negotiations for the Withdrawal of British Troops. When the Drummond Wolff convention was negotiated the Sultan refused to sign it, acting at the instigation of France and Russia. Count Montebello at that time pointed out the prejudice that he would receive as Calif and as Suzerain of Egypt if he assented to the condition that English troops should be permitted to re-occupy Egypt at any time when the British Government considered that peace and order were exposed to dangers from within or without. In March, 1890, Rustem Pasha, the Turkish minister in London, was instructed to re-open the negotiations, and in May he presented the draft of a convention. Lord Salisbury said that he was prepared to meet the wishes of the Turkish Government by fixing the conditions and the date for the evacuation of Egypt with the indispensable proviso that Great Britain shall have the right to intervene without further notice in the event of any external or internal danger arising, that the British Government shall be the sole judge of the necessity of re-entry, and that no other nation shall have a right to intervene in Egypt in any circumstances. Unless the Porte consented to these conditions and obtained beforehand satisfactory assurances that they would be acceptable to the powers the British Premier did not see the utility of discussing the question further. With this exchange of views the matter rested, as neither Turkey nor France was prepared to concur in the British standpoint. In a note to the powers in relation to the conversion the French Government called attention to the solemn declarations that had been repeatedly given that the occupation was only temporary and would cease as soon as order should be re-established in Egypt.

The Soudan. Khalifa Abdulla, the Baggara leader, supported by all the Baggara tribes and the Jaalins, has ruled the Soudan for years with grinding tyranny, under the pretense of maintaining a pure Mohammedan religion and the independence of the Soudanese from Egypt and Christian domination. Revolts occurred at various places, but they did not shake him in his position, and were easily put down by his Baggara emirs, who are aided by 70,000 well-armed troops. These live on supplies exacted from the more peaceable tribes. A detachment of this force threatened an invasion of Egypt in 1889, and was stopped by a British expedition to Toski. In 1890 no hostile demonstration of the dervishes was made on the Nile. Their advanced post was withdrawn in March to Dulgo, 170 miles from Wady Halfa. A famine was caused in 1889 by drought; 23,000 starving refugees arrived at Wady Halfa, and were relieved by the AngloEgyptian authorities, who have settled some of them on Government land. During the winter and spring Bisharis were driven in from the desert by lack of food and water. Commercial intercourse was opened at Assouan, but was not profitable, owing to the poverty of the Soudan. Unusually good crops in Sennaar, the granary

of the Soudan, lowered prices and put an end to the famine, except near Suakin and along the coast. In consequence of the scarcity the iron rule of the Khalifa has been weakened. A serious revolt broke out in the summer of 1890 in Darfur and Kordofan.

ENGINEERING IN 1890. With the exception of the bridge over the Firth of Forth, in Scotland, no engineering work of very great magnitude has been finished during the present year, though many considerable works are under way and promise early completion. The progress of some of these was seriously interrupted by the financial crisis of the autumn and early winter, but these difficulties have in most cases been overcome.

The Forth Bridge. The preliminary work on this stupendous structure was described in the Annual Cyclopædia" for 1885, page 328. The bridge was completed and formally opened on March 4, 1890. The construction was begun early in 1883, and the total cost up to the time of completion may be given in round numbers as $16,000,000. The following statistics are given in a paper on "The Bridge and its History," by Philip Phillips, one of the resident engineers: Total length, upward of 1 mile; cantilever arms projection (outer), 680 feet; depth of cantilevers over piers, 342 feet; depth at ends, 41 feet; distance apart of lower members at piers, 120 feet; distance apart of lower members at ends, 315 feet; diameter of largest tubes, 12 feet; top members, distance apart at vertical columns, 33 feet; top members, distance apart at ends, 22 feet; struts, largest diameter, 8 feet; ties, greatest length, 327 feet; central girder, span, 350 feet; central girder, depth at center, 51 feet; central girder, depth at ends, 41 feet; internal viaduct spans, various, 39 to 145 feet; total amount of steel in bridge, over 50,000 tons; south-approach viaduct, total length, about 1,980 feet; south-approach viaduct, average span, 168 feet; wind pressure allowed for, 56 pounds per square foot; depth of water in channels to be spanned, 218 feet; height of cantilever pier (masonry) above water, 209 feet; greatest air pressure in working the caissons, 32 pounds above atmosphere; weight on a single pier, 16,000 tons; thickest steel plates, 1 inch; length of plates used in tubes alone, 40 miles; greatest depth of foundations, 88 feet below high water; contraction and expansion allowed for, between 6 and 7 feet. The designers of the bridge were Sir John Fowler and Benjamin Baker, civil engineer, and the contractors for the construction were Messrs. William Arroll & Co.

Merchants' Bridge, St. Louis.-This bridge was completed and opened with suitable ceremonies on May 3. The superstructure is in three spans crossing Mississippi river. The approaches rest on piers consisting of four cylindrical columns. The eastern is in three deck spans of 125 feet each. The main trusses are 75 feet high in the center and 30 feet apart, providing room for two tracks, which are placed 12 feet apart. On the city side the approach is of three similar spans, beyond which a steel girder crosses one of the streets of the city, and there is about one quarter of a mile of trestle work. The bridge track is laid with steel rails secured to the ties by interlocking nuts, in order to prevent the

creeping of the rails. The bridge substructure includes four granite piers extending from a point 3 feet below low water to 2 feet above high water; above this latter point limestone is used, the whole resting upon caissons and the usual crib work. The first soundings were made in September and October, 1887, and the work was begun on the caissons in January, 1889. The depth of water at the piers was 18 feet when the caissons were sunk into position, but such are the changing conditions of the river that before the work was completed the depth had increased to 42 feet, and the force of the current was so great that the anchorages twice gave way.

Railway Bridge at Cincinnati.-This fine bridge forms an important link in the Chesapeake and Ohio system. Its interest as an engineering work is chiefly due to the length of the individual spans. There were no special difficulties in the way, excepting the necessity of avoiding obstructions to navigation. The central span is 550 feet between centers of piers and 84 feet between centers of cords: this is the largest truss span of this character that has been constructed. The two spans flanking the main channel are 490 feet each between pier centers, with 75 feet between centers of cords. These spans are all planned for a double-track railway with two roadways and two sidewalks: of course this renders it necessary to employ construction of the strongest and most durable description, and there is nothing, either in this country or in Europe, that shows such heavy, non-continuous trusses. All the main parts are of steel, and the bracing in the lateral and transverse systems, with the floor-beams and stringers, are of wrought iron. The system of connection between piers and posts is somewhat novel. All the connections are central and are designed so as to reduce sectional strains to a minimum. The system, which may be termed a web system, has been brought to its present perfection by the Phoenix Bridge Company. The total weight of the iron and steel in the three principal spans is 10,000,000 pounds. The approach on the Kentucky side is 1,533 feet, and on the Ohio or Cincinnati side nearly 2,300 feet, including the many tracks divergent to freight depots. The total structure, therefore, is one mile long, and more than 20,000,000 pounds of metal have been used in the entire work. ing the construction of this bridge several floods of exceptional height occurred, and large quantities of drift brought down on the current and lodging against the false work of the bridge often threatened its destruction. At one time the drift formed a continuous mass for more than 500 feet up stream from the bridge, and, in spite of every precaution, a large portion of already constructed work was swept away; fragments of the wreck were scattered for 50 miles down the river. To prevent a recurrence of such a disaster effective precautions were taken, and two lines of heavy piling were run up stream from each of the piers. These formed a V-shaped protection with the acute angle nearly 600 feet up stream. This protection proved to be a complete safeguard during several severe freshets. So actively was the work of repair prosecuted that five weeks after the day of the wreck the entire false work was replaced and regular work

Dur

resumed; this in itself is a very creditable feat of engineering, aside from anything in connection with the permanent structure.

It was necessary to sink caissons for the piers on both sides of the channel. These were made in the usual way, each containing more than 500,000 feet of timber. The caissons were both launched and placed in position in 1887, and complete pneumatic machinery and an electriclight plant were placed on two barges and constantly maintained alongside the caissons. As the caissons descended and the air-pressure increased, some difficulty was encountered in rendering the atmosphere endurable for the workmen. Many large bowlders, rocks, etc., were encountered and were hoisted through the excavating shafts. A solid concrete wall was built in the middle of one of the caissons at a weak point, and the foundations were finally made as absolutely secure as such a work can possibly be.

North Sea and Baltic, or Holstein Canal. -For many years the military necessity of a ship canal between the Baltic and North Seas has claimed the attention, first of the Prussians and Danes, and later of the consolidated German Empire. There are already three small canals between the two seas. One of them, the oldest in Europe, was built in the thirteenth century and is still in use. Another was constructed in the sixteenth century, and a third in the eighteenth, having been completed by King Christian of Denmark in 1785. But none of these are true ship canals. The total length of the completed canal will be between 60 and 61 miles, special attention being given to the construction of easy curves, with radii of 5,000 and 6,000 feet. Especial attention is given to this feature, as it is of the highest importance that large steamers shall be able to pass without hindrance around any of the curves at a uniform rate of speed. This purpose is further facilitated by the fact that the canal is a through cut, having merely tidal locks at either end. The mean range of tides in the Baltic is 1 foot 8 inches above and below the canal level, and in the Elbe 4 feet 6 inches above the same level. This last, of course, gives a surplus of water at certain hours of the day, which must be controlled by locking arrangements. The canal was formally inaugurated. not opened, by the German Emperor in June, 1887. The line passes from the Elbe through swampy land, gradually rising to the height of 82 feet above the sea; the descent thence leads to the Eider river, taking advantage of a natural chain of lakes, until it reaches the old Eider canal, which has been enlarged. At Brunsbuttel, on the Elbe, there will be three locks of different sizes, the largest 1,180 feet long by 196 feet wide. At the Baltic one large lock will serve for vessels of all sizes. The machinery will be worked by hydraulic power. Several railroads and highways cross the canal on drawbridges. The total estimated amount of excavation is 67,000,000 cubic yards, and the estimated cost of the entire work is $39,000,000. This sum is considerably in excess of what would be required in a canal intended merely for commercial uses; something like a third of the cost is necessarily added to make it practicable as a military work. The estimated annual cost of maintenance is somewhat less than $500,000. Vessels coming from England save in distance,

time, and pilot dues, the long voyage around Denmark being avoided. This saving, in some cases, will be as much as 425 miles, which means from twenty-five to thirty hours for steamers, and about four days for sailing vessels. Another unknown quantity must also be considered, since, on an average, 200 vessels are annually wrecked in the North Sea, and of these the canal may save a large percentage. The North Sea and Baltic traffic is variously estimated from 35,000 to 40,000 vessels annually, the aggregate registration exceeding 12,000,000 tons.

The Manchester Ship Canal.-This is now so near completion that it may be regarded as one of the engineering works of 1890. From the first proposition contemplating the building of this canal, considerable opposition was made by the commercial interests of Liverpool and along the Mersey river, because it will undoubtedly reduce the importance of Liverpool as a port of entry. This opposition worked so efficiently in Parliament that the passage of the canal bill was delayed for several years. In 1887 it was overcome, and since then the work has been prosecuted vigorously. The contract time for its completion was four years. In total length the canal is somewhat more than 35 miles from the Mersey to the city of Manchester. Its completion will practically make one of the great inland manufacturing centers of England a seaport, readily accessible through the tidal estuary of the Mersey. The canal naturally divides itself into a tidal section, that from Eastham through the Mersey to Runcorn, thence 8 miles inland, with a bottom width of 100 feet and a depth of 26 feet at low water. The second section, the canal division proper, from Warrington to Manchester, is 15 miles, with the same dimensions and a surface width of 300 feet. There are four sets of locks, in groups of three, with intermediate cuts, so that any vessel in existence may be passed without waste of water. The greatest elevation of the canal is 60 feet. The total amount of excavation is about 48,000,000 cubic yards, and the contract price of the work is $30,000,000; 15,000 men, 70 steam shovels, 50 steam cranes, 150 locomotives, and several thousand cars have been constantly employed, the average monthly record being about 1,000,000 cubic yards. The engineering work throughout has been organized with the greatest precision.

The Corinth Canal.-Historically this is one of the most interesting canals in existence. A narrow isthmus separating the waters of the Egean Sea and the Gulf of Lepanto tempted the early canal makers as long ago as 628 B. C. Surveys were made some centuries later across the isthmus, and the Emperor Nero actually began the work. Evidences of these early excavations are still visible on both sides of the isthmus. But the high elevation of the central plateau prevented the completion of these early works. The present canal, now approaching completion, was begun in May, 1882, the King of Greece turning the first sod with due ceremony, and the Queen setting off the train of dynamite mines. The canal will be 4 miles long, with a surface width of about 92 feet and a bottom width of 52 feet. The depth will be 28 feet, making it available for vessels of the deepest draught. The depth of cutting at the highest part of the isth

mus will be 228 feet. Lack of funds and defective organization have rendered the progress of the work slow, when compared with similar works driven by modern machinery under competent direction. A maximum force of about 3,000 men has been employed, with 15 locomotives, 700 cars, and 6 or 8 dredges. The largest day's work was about 10.000 cubic yards, and the total estimated amount of excavation will be somewhat in excess of 11,000,000 cubic yards. The line of the canal is perfectly straight, and about 4 miles from gulf to sea. The original contract contemplated the expenditure of $5,280,000, but this proved inadequate, and the total cost will probably be about $12,000,000. This canal will shorten the voyage from Turkey in Asia into the Adriatic Sea by 185 miles, and for vessels coming through the Straits of Messina by 95 miles. It is estimated that 4,500,000 tons will annually make use of the canal.

Separable Ships.-An ingenious system of ship construction has been introduced on the Great Lakes. A large steamer, the "Mackinaw," of 3,578 gross registered tonnage, was finished in October by the Steel Steamship Company, of Saginaw, Mich. The vessel is 290 feet long, 41 feet bottom, and 26 feet molded depth. She is of steel throughout, and is a double-bottomed water-ballast vessel, designed to class A1 for twenty years. The peculiarity in construction is that she is designed to be taken apart amid-ships, so that she can pass through the locks of the Welland and other canals, and be put together again on reaching Montreal. In point of fact, she left the building yard under her own steam, and was put in dry dock on reaching Buffalo. A row of rivets was cut out all around her midship section, and the two halves were separately floated out of dock. The after half proceeded, stern foremost, under its own steam, to the canal; while the forward section was towed by two ordinary tug boats and kept company with its better half, through Lake Ontario and the lower canal, until the two could be rejoined at Montreal, whence the vessel went to sea as a complete ship. The owners of the ship are F. W. Wheeler & Co., of West Bay City, Mich., and the work of construction, disconnection, etc., was conducted under the superintendence of Mr. Williams, a member of the firm.

Marine Engineering.—The steamer "Ulunda," of 1,800 tons, went ashore on Aug. 26 at Brier Island, in the Bay of Fundy. Her bottom plates were badly stove on rocks, and she was considered a total loss, and, having been abandoned by the underwriters, she was sold where she lay to a Halifax company for $3,000. Shortly afterward she was still further damaged by a storm, all the bottom plates forward of the engines being knocked off. The purchasers bolted pine planks to the under side of the second deck, calked them, and at low tide placed 1,200 empty casks in the hold; as the tide rose, the vessel floated. She was towed to Westport, where she was beached and fitted with a temporary wooden bottom, and proceeded thence under her own steam to Halifax, where she has been repaired.

Another noteworthy case of marine engineering is that of the British war-ship "Sultan," which ran upon an uncharted rock near Malta. She sank in water of such depth that all her

deck works were submerged. Several unsuccessful attempts were made to raise her, her great size rendering ordinary appliances unavailing. Her displacement when armed and loaded is 9,200 tons. She is 325 feet long, 59 feet beam, and ordinarily draws 27 feet of water. When sunk she had her full battery of eight 18-ton muzzle-loading guns on board, and four 124-ton guns, besides the usual complement of breechloading and quick-firing guns. Observations of divers show that the starboard side of the ship was indented in all directions, the plates being in many cases forced up through the double bottom, and the longitudinal frames twisted in every direction. The difficulty of floating the ship, even after her battery was removed, was increased by the fact that she was literally wedged between two beds of rock, so that portions of the rock had to be blasted away before the divers could examine parts of the hull. This was finally accomplished, and the openings were temporarily stopped by means of wood, canvas, and oakum, a new cement being used which hardened under water to the consistency of putty, and made temporarily tight some of the rents that could not otherwise have been stopped. This done, the ship was successfully pumped out, floated, towed to Malta, and eventually taken to England for repairs.

New Docks at Southampton, England.The Southampton Dock Company has been in existence since early in the present century. It began its first docks in 1838, and opened them for business in 1844. Since then the shipping requirements of the port have largely increased and compelled additions to the docking facilities of the company. The docks are at the mouth of the river Itchen, and, as originally designed, afforded ample accommodations for the shipping of that period. There is a curious phenomenon of double tides at this port. In addition to the usual regular tidal movements, there is a second high water about two hours after the first. This is accounted for by the peculiar conformation of this part of the coast, and has to be considered in the construction of docks. The new deep-water dock, opened by the Queen on July 26, has an area of 18 acres; it is of an irregular quadrangular shape, the northwest and northeast and southwest wharves being 850 feet long each, and the southeast wharf 800 feet. The entrance, opening to the southeast, is 175 feet wide, with side walls 200 feet long. At low water there is 26 feet of depth in all parts of the dock, so that the largest 'vessels likely to be built for many years to come can be safely moored alongside the wharves, with direct connection by rail in all cases. Alfred Giles has had charge of the work as superintending engineer.

The Ferry Boat "Bergen.”—A new type of ferry boat has lately been placed in service on the Hudson river, between New York and Hoboken. In size she does not differ materially from the ordinary paddle-wheel boats used in this neighborhood. The novelty of her construction consists in a long propeller shaft running lengthwise of the boat and provided with a screw at either end. The propellers, therefore, are rotated together, one pulling and the other pushing, a single compound engine driving the machinery. The advantages claimed are, first, that the engines

and boilers are all below deck, so that the space usually occupied by them is saved for passengers and teams. The estimated saving in these respects amounts to about 20 per cent., the room being chiefly gained for trucks and carriages. The absence of the side wheels also opens the passenger cabins throughout the length of the boat, the troublesome narrow passage between the cabins fore and aft being done away with, increasing the capacity for passengers about 35 per cent. Many attempts have previously been made to employ boats with propelling screws at both ends, but heretofore they have not been very successful. The "Bergen "has been in use for some months, and appears to fulfill all that was expected of her. It has been found that one of the chief obstacles to feriy navigation in this latitude is the accumulation of ice in the ferry slips. This ice, when it is ground up into small and partly spherical pieces, forms to a great depth in the slips, and paddle wheels are often powerless to overcome its resistance. It has been customary for the ferry companies to keep tug boats with screw propellers on purpose to drive the ice out of the slips, so that the paddle-wheel boats could do their work. The new boat with a screw at either end, both working in the same direction, creates powerful submarine currents, which carry the ice toward the

coal and iron from the west Superior region down to the lower lakes. Capt. Alexander McDougall is the designer of what are known as whale-shaped freight carriers, a considerable number of which are already in service on the lakes. He has lately constructed a tow steamer especially designed for handling these barges. She is similarly shaped and carries a powerful engine, and it is estimated that in fair weather she can tow as many as 100 of the barges referred to. Should these expectations be sustained, this may revolutionize the coal and iron-ore trade of the lakes, since it would probably largely underbid the present steel and wooden ships in this line of business.

The St. Clair River Tunnel.-The enormous increase of traffic over the Grank Trunk Railway, of Canada, and the connecting lines in the United States, made it obvious several years since that other means of transit than a steamcar ferry were necessary across St. Clair river. Surveys were made contemplating the construction of a bridge; but, owing to the extreme flatness of the country on both sides, this was found impracticable, because of the great height necessary to allow free navigation in the river. Moreover, the current is so swift (eight miles an hour, at times,) that any possible structure in the nature of a bridge would be liable to damage when

stern of the boat and empty the slip of ice in a few minutes. A series of preliminary experiments, comparing the efficiency of this new type of boat with the old side-wheelers, gave results favorable to the new type, both in consumption of coal and in speed. An additional advantage may perhaps be taken into account as suggested in a paper read by Capt. Zalinsky before the Naval Institute, in which he emphasizes the utility of ferry boats for harbor defense, saying that the pneumatic dynamite guns may be mounted on them. Their light draught, great strength, and good speed would render them very effective for coast-wise operations. The wide, overhanging guards would render it possible to introduce armor of some kind, so that the boats could be protected against torpedoes. The typical ferry boat was used extensively during the civil war, and proved highly efficacious for river service.

Towing Steamers. It is within comparatively few years that it has been discovered that a steam engine of given power can do a great deal more efficient work when set up in a tow boat than when placed independently in a large vessel. The development of towing has made rapid progress in the Great Lakes of late years, and tow barges of a new model have been introduced, devoted mainly to the transportation of

the ice broke up in the spring. At length the construction of a tunnel was decided upon, to cross the river from Port Huron, Mich., on the American side, to Sarnia, on the Canadian side. A company was formed in 1886, test borings were taken on both sides of the river, and attempts were made to begin the main tunnel by sinking large preliminary shafts. These shafts soon entered a stratum of soil that seemed to be a mixture of clay and quicksand. It was so very difficult of management, and the pressure on the sides of the shafts was so tremendous, that at last they had to be abandoned and filled up with sand in order to prevent dangerous subsidence of the surface under adjacent buildings. Excavations were then begun to approach the tunnel entrance by a gently inclined plane, and when a sufficient depth was reached Beach hydraulic shields were introduced, and the work proceeded with remarkable dispatch. These shields were designed by Alfred E. Beach, of the "Scientific American," and patented in 1869. The first excavation was made under the steeets of New York, with a view to an underground railway: but that design was abandoned, and only an experimental tunnel was constructed. The St. Clair Tunnel has now so nearly approached completion that it may be counted as one of the