The Encyclopedia britannica; a dictionary of arts, sciences, and general literatureWith new maps, and original American articles by eminent writersWith American revisions and additions, bringing each volume up to date . st tunnel in the world,being more than 3i miles in length, and was driven underMonte Salviano, which necessitated shafts no less than 400feet in depth. Forty shafts and a number of cunicixlior 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 feefr highby 6 feet wid
The Encyclopedia britannica; a dictionary of arts, sciences, and general literatureWith new maps, and original American articles by eminent writersWith American revisions and additions, bringing each volume up to date . st tunnel in the world,being more than 3i miles in length, and was driven underMonte Salviano, which necessitated shafts no less than 400feet in depth. Forty shafts and a number of cunicixlior 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 feefr 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 pickaxesorhammer 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. Tig. 1 —Method of mining, 1621. {,FTom De ReMetaUica,Biise\,l621.}shaking cloths in the headings and by placing inclinedboards at the top of the shafts are also on record. In1766 a timnel 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 railways tunnel-ling became one of the ordinary incidents of a contractorswork ; probably upwards of 4000 railway tunnels havebeen executed. Subaqueous Tumielling. — In 1825 Brunei commenced and in1843 completed the Thames tunnel, which was driven at pointsthrough liquid mud by the aid of a shield at a cost of about£1300 per lineal yard. It is now used by the East London 1872 Chesboro
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