The work of blowing up the masses of rock which form the dangerous rapids known as the Iron Gates, on the Danube, was inaugurated on September 15, 1890, when the Greben Rock was partially blown up by a blast of sixty kilogrammes of dynamite, in the presence of Count Szapary, the Hungarian premier; M. Baross, Hungarian minister of commerce; Count Bacquehem, Austrian minister of commerce; M. Gruitch, the Servian premier; M. Jossimovich, Servian minister of public works; M. De Szogyenyi, chief secretary in the Austro-Hungarian ministry of foreign affairs; and other Hungarian and Servian authorities. Large numbers of the inhabitants had collected on both banks of the Danube to witness the ceremony, and the first explosion was greeted with enthusiastic cheers. The history of this great scheme was told at the time the Hungarian Parliament passed the bill on the subject two years ago. It is known that the Roman Emperor Trajan, seventeen centuries ago, commenced works, of which traces are still to be seen, for the construction of a navigable canal to avoid the Iron Gates.

For the remedy of the obstruction in the Danube, much discussed of late years, there were two rival systems - the French, which proposed to make locks, and the English and American, which was practically the same as that of Trajan, namely, blasting the minor rocks and cutting canals and erecting dams where the rocks were too crowded. The latter plan was in principle adopted, and the details were worked out, in 1883, by the Hungarian engineer Willandt. The longest canal will be that on the Servian bank, with a length of over two kilometers and a width of eighty meters. It will be left for a later period to make the canal wider and deeper, as was done with the Suez Canal. For the present it is considered sufficient that moderate sized steamers shall be able to pass through without hindrance, and thus facilitate the exchange of goods between the west of Europe and the east.

The first portion of the rocks to be removed, and of the channels to be cut, runs through Hungarian territory; the second portion is in Servia. The new waterway will, it is anticipated, be finished by the end of 1895, and then, for the first time in history, Black Sea steamers will be seen at the quays of Pesth and Vienna, having, of course, previously touched at Belgrade. The benefit to Servian trade will then be quite on a par with that of Austria-Hungary. Even Germany will derive benefit from this extension of trade to the east. These, however, are by no means the only countries which will be benefited by the opening of the great river to commerce. Turkey, Southern Russia, Roumania, and Bulgaria, not to speak of the states of the west of Europe, will reap advantage from this new departure. England, as the chief carrier of the world, is sure to feel the beneficial effects of the Danube being at length navigable from its mouth right up to the very center of Europe.

The removal of the Iron Gates has always been considered a matter of European importance. The treaty of Paris stipulated for freedom of navigation on the Danube. The London treaty of 1871 again authorized the levying of tolls to defray the cost of the Danube regulation; and article 57 of the treaty of Berlin intrusted Austria-Hungary with the task of carrying out the work. By these international compacts the European character of the great undertaking is sufficiently attested.

THE "IRON GATES" OF THE DANUBE.

The work of blasting the rocks will be undertaken by contractors in the employ of the Hungarian government, as the official invitation for tenders brought no offers from any quarter. The construction of the dams, however, and the cutting of several channels to compass the most difficult rocks and rapids, will be carried out by an association of Pesth and other firms. The cost, estimated altogether at nine million florins, will be borne by the Hungarian exchequer, to which will fall the tolls to be levied on all vessels passing through the Gates until the original outlay is repaid.

Very few persons know, says the American Architect, what an enormous work has been undertaken at the Iron Gates of the Danube, where operations are rapidly progressing, mainly in accordance with a plan devised many years ago by our distinguished countryman, Mr. McAlpine. The total length of that part of the river to be regulated is about two hundred and fifty miles, so that the enterprise ranks with the cutting of the Panama and Suez canals as one of the greatest engineering feats ever attempted. Work has been begun simultaneously at three points: at Greben, where there are reefs to be taken care of; at the cataract, near Jucz, and at the Iron Gate proper, below Orsova. At Greben, where the stream is shallow, but swift, a channel two hundred feet wide is to be blasted out of the rock, and below it a stone embankment wall is to be built more than four miles long. From a reef which projects into the river a piece is to be blasted away, measuring five hundred feet in length, and about nine feet in depth. The difficulties of working in this part of the river are very great. Not only is the current extremely rapid, but in certain places ridges of rock barely covered at low water alternate with pools a hundred and forty feet deep, which give rise, in the rapid current, to frightful whirlpools and eddies.

These deep pools are to be filled at the same time that the reefs are cut away, and it is estimated that nearly three million cubic feet of loose stonework will be needed for this purpose alone. In addition to the excavation, artificial banks and breakwaters, for modifying the course of the stream, are to be built; so that it is estimated that the masonry to be executed in this section will amount to about five and one-half million cubic feet.

In the cataract section, at Jucz, a channel two hundred feet wide, and more than half a mile long, is to be blasted out of the rock, and a breakwater built, to moderate the suddenness of the fall. This breakwater is to be about two miles long, and ten feet thick at the top, increasing in thickness toward the bottom. The rock in which the channel must be cut at this point is partly serpentine greenstone, partly chrome iron ore, and is intensely hard. In the section of the Iron Gate, the work to be done consists in "canalizing" the river for a distance of a mile and a half, by building a wall on each side, and excavating the bed of the river between. The channel between the walls will be two hundred and fifty feet wide. It is estimated that nearly three million cubic feet of rock will have to be excavated here, all of which will be used to fill in behind the embankment walls. Of course, the greater part of the rock will be removed by means of blasting with high explosives, but some of it is to be attacked with a novel instrument, which was first tried, on a small scale, on the Panama Canal, and is to be used for serious work here. This instrument, as it is to be employed on the Danube, consists of an enormous steel drill, thirty-three feet long, and weighing ten tons.

By means of a machine like a pile driver, this monstrous tool is raised to a height of about fifty feet, and allowed to drop, point first. So heavy a mass of metal, falling from a considerable height, meets with comparatively little resistance from the water, and the point shatters and grinds up the rock on which it strikes. Fifty or sixty blows per minute can be struck with a tool of this kind, and ten thousand blows in all can be inflicted before the tool is so worn as to be past service. Several of these drills will be at work at the same time, and to remove the fragments of rock which they break off, a huge dredge of three hundred and fifty horse power is to be employed. For excavating by means of explosives, arrangements have been made for drilling the holes for the cartridges with the greatest possible rapidity, as on this depends the celerity with which the work can be pushed forward. Much of the work will be done by means of diamond drills, which are mounted on boats. Five of these boats have been provided, each with seven diamond drills, arranged so as to work perfectly in twenty feet of water. Other boats are fitted with pneumatic drills, which are operated by means of air, compressed to a tension of seven hundred and fifty pounds to the square inch.

The pressure of the compressed air is transmitted by means of water to the drills, which act by percussion, and work very rapidly. These drills are curiously automatic in their operation. After boring the holes to the allotted depth, the machine automatically sets in each a tube, washes out the dust, inserts a dynamite cartridge, withdraws the tube, and connects the wire of the electric fuse in the cartridge with the battery wire in the boat. The cartridges are charged with a pound of dynamite to each. In hard rock only one charge is fired at a time, but in softer material four are fired at once. If the water over the work is deep, the boat is not moved from its position, but in shallow water it is towed a few yards away from the spot where the explosion is to take place. The drill holes are about six feet deep, and are spaced at the rate of about one to every three square feet, something, of course, depending upon the character of the rock. The whole work is now under contract, the mechanical engineering firm of Luther, of Brunswick, having undertaken to complete it in five years, for a payment of less than four million dollars.