Other Important should be made of the Stand Edge Tunnel ( about three miles long), the Kilsby (one and two-fifth miles), in England; the De la Nerthe (two and one-tenth miles); the Blasy (two miles), on the Paris, Lyons, and -Marseilles Railway, in France; and the Hauenstein tunnel (one and two-fifth miles), in Switzerland. In Germany and Austria, except the several Alpine tunnels above described, there are comparatively few long tunnels.
The following tabulation relating to the four principal tunnels of the world may be interesting for reference: These figures exhibit at a glance the decided progress that has been made in the art of tunnelling, in the cheapening of the cost of such engi neermg worKs, ana me greater rapidity WIIII WIIICII lt IS now possinie to construct them with the aid of improved machinery, as compared with the engineering possibilities of a few years ago.
Projectea' double railway tunnel under the Hudson River at New York has been partially constructed, though at the time of this writing work thereon has been temporarily suspended. The fact is note worthy that the plan was attempted of carrying the work forward beneath the river in yielding material (silt, or river-mud) without the use of bulk heads, compressed air at the working headings being solely relied upon to keep the earth in place. A disaster involving the loss of a number of lives compelled the abandonment of this questionable mode of operation.
English Channel project of much greater magnitude than any heretofore referred to has been mooted for several years, and the results obtained from a eonsiderable amount of preliminary work appear to have demonstrated its entire feasibility. This is nothing less than the driving of a tunnel beneath the bed of the English Channel to connect England and France. The termini would be in the neighborhood of Dover, on the
English coast, and of Calais, on the French side. The advantage of the proposed tunnel for the transport of merchandise without breaking bulk is fully recognized, but political considerations have prevailed thus far to prevent its completion.
Una'ergrouml Raihew), are used to some extent for underground railroads in cities. In London a very extensive system of this kind is in operation, which in respect of the magnitude of its traffic far surpasses that of any system of rapid transit in use in any other city of the world. London Engineering thus referred to it some years ago: "In Lon don the underground-railroad system has been in operation eleven years, and so great has been its success, so fully does it meet the requirements of the population, that every year adds to its extension. Opened in 1363 with a section of four and one-half miles from Bishop's Road to Farringdon Street, it has been considerably extended, until now 0373) it has a length of thirteen miles, while new extensions are in process of construction. Many millions of passengers are annually conveyed over these underground tracks, which extend beneath the streets in all directions, uniting the principal centres of trade, intersecting all the great railway-lines, and by the marvellous facility for traffic facilitating the enormous transactions of daily business for which London is so renowned." At the present time (1388) there are fifty miles of underg-round railway in operation in London, carrying the extraordinary number of fifteen million five hundred thousand passengers per mile per annum. On Plate 26 (jig. 23) are shown the cross section of the tunnel and one of the stations of the underground railway of London.