. The Encyclopaedia Britannica; ... A dictionary of arts, sciences and general literature . est tunnel in the world,being more than 3 J miles in length, and was driven underMonte Salviano, which necessitated shafts no less than 400feet in depth. Forty shafts and a number of cuniculior inclined galleries were sunk, and the excavated materialwas drawn up in copper pails, of about ten gallons capacity,by windlasses. The tunnel was designed to be 10 feet highby 6 feet wide, but its actual cross section varied. It isstated that 30,000 labourers were occupied eleven years inits construction. With mo
. The Encyclopaedia Britannica; ... A dictionary of arts, sciences and general literature . est tunnel in the world,being more than 3 J miles in length, and was driven underMonte Salviano, which necessitated shafts no less than 400feet in depth. Forty shafts and a number of cuniculior inclined galleries were sunk, and the excavated materialwas drawn up in copper pails, of about ten gallons capacity,by windlasses. The tunnel was designed to be 10 feet highby 6 feet wide, but its actual cross section varied. It isstated that 30,000 labourers were occupied eleven years inits construction. With modern appliances such a tunnelcould be driven from the two ends without intermediateshafts in eleven months. No practical advance was made on the tunnelling methodsof the Romans until gunpowder came into use. Old en-gravings of mining operations early in the 17th centuryshow that excavation was still accomplished by pickaxesor hammer and chisel, and that wood fires were lighted atthe ends of the headings to split and soften the rock inadvance (see fig. 1). Crude methods of ventilation by. Fig. 1.—Method of miniug, 1621. (From i>«iJ«il/e(oiKcff, Basel, 1621.)shaking cloths in the headings and by placing inclinedboards at the top of the shafts are also on record. In1766 a tunnel 9 feet wide, 12 feet high, and 2880 yardslong was commenced on the Grand Trunk Canal, England,and completed eleven years later; and this was followedby many others. On the introduction of raihvays tunnel-ling became one of the ordinarj incidents of a contractorswork; probably upwards of 4000 railway tunnels havebeen executed. Subaqueous Tunnelling. — In 1825 Branel commoDccd and in1843 completed the Thames tunnel, which was driven at jiointsthrough liquid mud by the aid of a shield at a cost of about£1300 per lineal yard. It is now used by tlie East London 1872 Chesborough began tunnelling under the Detroit river,between Canada and iliohigan, , but the work was abandonedowing to co
Size: 1613px × 1548px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookidencyclopaedi, bookyear1902
