The most notable of the many other exam ples of mountain tunnels are: the "Stone Moun tain Tunnel," at Gibraltar, a series of galleries three miles long, pierced for cannon at inter vals of 12 yards and having guns of large calibre already mounted in 1,000 of these em brasures. The "Joseph II Mining Adit," form ing the main efflux gallery of the metal and sulphur mines at Schemnitz, Hungary. It was begun in 1782, the time required for con struction being estimated at 30 years and the cost at 1,215,000 florins. The progress of the work, however, suffered a great many delays and it was not completed until 1878. the total expenditure amounting to 4,599.000 florins. It is 9 feet 10 inches high, five feet two inches wide and is the longest mining tunnel in the world, having a length of miles. The IlKojak," forming a part of the Northwestern State Railway of India, about two and one-half miles long, and completed in 1891. The aTequixquiac," a boring 14 feet in diameter, driven through sandstone for the purpose of draining the Valley of Mexico. It is six miles long and cost $6,760,000. The drainage works designed to improve the sanitary condition of the City of Mexico and prevent the inundation of its streets, for long periods at a time, by the overflow from Lake Texcoco and the con sequent loss of thousands of lives, were begun during the latter part of the 16th century. Up to 1789 the work was of an intermittent char acter, cost many thousands of lives and many millions of dollars. From 1789 to 1830 the effort was more sustained and systematic but, although $8,000,000 had been expended, and the city protected from the inundations, its position in the bottom of a basin without natural drain age, with the artificial drainage canal inade quate in depth owing to its being controlled by the level of the lake which was but slightly lower than that of the city, continued to keep it subject to virulent epidemics of malaria. The new works, gigantic in character and ranking with the greatest of modern engineering accom plishments, were begun in 1885 and completed in 1900, with a total expenditure of $20,000,000. These works consist of a complete sewerage system within the city; a system of sewers to control the overflow of the entire valley; a canal 43 miles long, connected with the sewer age system, at the Saint Lazaro gates, by which the sewage of the city, its waste waters and the waters of the valley are conducted to the tun nel, thence to a river emptying into the Gulf of Mexico.
The on the Bergen Railway in Norway, about three and one-third miles in length, and the Yanagase Zama forming a part of the Tsuruga-Nagahama Railway in Japan.
Two London river tunnels deserve mention. The Blackwell tunnel under the Thames is a mile and a quarter in length, but only 3,088 feet are under the river, 1,370 feet are roofed over and the remainder of the length is com posed of the open-cut entrances. It was driven with a 28-foot shield and built of great cast iron rings steadied with cement. The Rother hithe under the Thames is about the same size.
New York River This article would not be complete without reference to the great under-water tunnels constructed around Manhattan Island during the opening years of the century. The greater part of New York city lies on Manhattan Island and to afford easier railway communication from all sides a series of very difficult under-river tubes was planned and built. The four largest were built by the Pennsylvania Railroad Company, to bring its traffic into New York from jersey City and to carry it over the East River to Long Island. The Hudson and Manhattan Railroad system built four under the Hudson tor passenger communication between New Jersey and New York, affording an outlet for the passengers of the Lackawanna and Erie railways and also for Pennsylvania passengers from Newark and local points. The pair of Belmont tunnels was constructed to connect Long Island City with New York and open up Queens County to de velopment. The Rapid Transit tunnels run from the Battery in Manhattan to Joralemon street, Brooklyn. Two other pairs of tunnels are under construction to join Manhattan and Brooklyn. No other great city was ever so thoroughly honeycombed by tunnels. See NEW