Mr. Doherty throws light on the long, grim history of tunnels by telling the reader precisely how to survey the route through a mountain, how to measure the slope of land between entrances, and other particulars necessary to appreciate the accomplishments of early and late engineers. In this respect, and in currency, his book has a considerable advantage over its competitors. It is also thorough in relating tunnel building to developments in transportation generally. Thus, tunnels were revived when canals became popular (water couldn't go uphill), again with the coming of the railroad (also hampered by height). Technology is similarly interrelated; the Roman method of sinking shafts from the surface for ventilation sufficed until time to tunnel through the Alps; then compressed air made it possible to drill and ventilate and cool at the same time (and another novelty, dynamite, speeded the seemingly endless job). A final factor is geology, explained, like the other aspects, via numerous diagrams. All of this is shaped into a coherent consecutive account of great tunnels, typical tunnels, unusual tunnels, up to the English Channel scheme that's presently being considered. In sum, the sort of book that freshens a familiar experience.