Page:The American Cyclopædia (1879) Volume XVI.djvu/47

TUNNEL cast in 9-foot sections, of 9 ft. internal diame- ter and 2J in. thick, was then lowered within the crib to the bottom of the lake; and this cylinder was connected with the land two miles distant by a tunnel under the lake bottom. Gate wells were constructed in the sides of the crib, and after the completion of the tunnel the top section of the cylinder, extending above water level, was removed, and the water ad- mitted through a screen. The tunnel, of cir- cular cross section, was driven through a stiff blue clay ; diameter of excavation 5 ft., subse- quently lined with two rings of brick. The final cost in full to the city was $457,844. Ac- cording to the statements and books of the contractors, the items were: crib and outer shaft, $117,500; land shaft, $12,000; tunnel proper, $195,000; total, $324,000. The balance of the expenditure was used in necessary con- tingencies. For full details of this work see " Eighth Annual Eeport of the Board of Pub- lic Works " (Chicago, 1869) ; also a r'eport of Prof. W. P. Blake, commissioner of California to the Paris exposition (1867). A second tun- nel, 7 ft. in diameter, extending to the same crib, was completed in July, 1874, at a total cost of $411,510; and two tunnels for traffic have been constructed under Chicago river. A tun- nel under Lake Erie, at Cleveland, Ohio, be- gun in August, 1869, finished in March, 1874, is similar in plan, purpose, and construction to the one first driven under the lake at Chi- cago, except that much greater difficulties were encountered in its construction, from meeting several bodies of very soft ground. It is 6,606 ft. in length, and the total cost amounted to $320,352. It was estimated by Capt. Tyler in 1873 that between 300,000 and 400,000 per- sons yearly crossed the English channel at Do- ver, that the number was constantly increas- ing, and that if a tunnel were built it would probably be doubled. The idea of a tunnel under the channel was first broached by M. Mathieu, a French engineer, who laid plans for one before Bonaparte in 1802. Owing to the subsequent disturbances the projector and his plans were lost sight of. Subsequently S'ans were proposed by M. Thome de Gamond, r. Payerne, Messrs. Franchot and Tessier, Favre, Mayer, Dunn, Austin, Sankey, Boutet, Hawkins Simpson, Low, Boydon, Brunlees, "Waenmaker, and others. To M. Thome de Gamond is conceded the credit of pushing the project to its present advancement. In 1872 the present channel company was incorporated, Sir John Hawkshaw, Mr. James Brunlees, and M. Thome de Gamond being appointed the en- gineers. The route finally adopted places the tunnel on a line drawn from St. Margaret's bay near the South Foreland, on the English side, to a point between Sangatte and Calais in France. The total proposed length of the tunnel is 31 m., of which 22 m. will be under the channel. Should the preliminary tests prove favorable, it is proposed to begin the actual construction by sinking shafts on either shore to the depth TUNNY 39 of 450 ft. below high-water mark. Driftways will be driven from the bottom of these for the drainage of the subsequent tunnel proper. The tunnel, if constructed, is to begin 200 ft. above the driftway, and will be driven from both ends. It is to be through the chalk, and in no part of it will there be less than 200 ft. of ground between the crown of the arch and the bed of the channel. It will be on a down grade of one foot in 80 to the junction of the drainage driftway, and then on an up grade of one in 2,640 to the middle of the strait. It is proposed to drive the driftway or heading with Dickinson Brunton's machine for tunnel- ling through chalk, which works lite an auger boring wood. It is believed, from actual work done, that this machine will advance at the rate of from a yard to a yard and a quarter an hour. At this rate it would require two years to construct the driftway, driving from either end, at an estimated cost of 800,000. After the heading has been driven through, it has been estimated that four years' time and an outlay of 4,000,000 will finish the work, in- cluding arching ; but Sir John Hawkshaw and his associates consider it best, before begin- ning the work, to double this figure as an es- timate. The preliminary works to be under- taken are the sinking of two shafts at either extremity of the tunnel, from which an ordi- nary mining driftway is to be driven about half a mile out under the sea, the cost of which is estimated at 160,000. This done, the engi- neers will be better able to judge of the ulti- mate practicability of the work. See Lehrbuch der gesammten Tunnelbaulcunst, by F. Eziha (6 vols., Berlin, 1865- 1 72) ; and I)er Tunnelbau, by J. G. Schon (4to, Vienna, 1866). There is no complete work in English on modern tun- nelling. The facts in this article are largely drawn from a practical treatise on American and European tunnelling, now (1876) in course of preparation by Henry S. Drinker, E. M., of Philadelphia. TMNY, a marine fish of the mackerel family, and genus thynnus (Cuv.). The body is elon- gated and compressed, with a slender tail keeled in the middle, and with two oblique cutaneous folds at the base of the caudal fin on each side ; mouth large, with the teeth small, awl-shaped, in a single row on each jaw, and fine and crowded on the vomer and palate ; there are two dorsals, near together, the posterior fol- lowed by nine or ten finlets opposite those of the anal fin ; scales largest around the pectoral region, forming a kind of corslet, on the an- terior part of the back, and along the lateral line ; cerebellum remarkably large. The com- mon tunny of Europe ( T. milgaris, Cuv.) attains a length of 15 to 20 ft., and a weight of more than 1,000 Ibs. ; it is dark blue above, the cors- let lighter, sides of head white, and below grayish white spotted with silvery ; first dorsal, pectorals, and ventrals black, the other fins mostly flesh-colored ; the pectorals are scythe- shaped, and one fifth the length of the body.