Engineering Wonders of the World
Volume III

352 ENGINEERING WONDERS OF THE WORLD. SNOW PROTECTION AGAINST VERTICAL SNOW FALL. kept in good condition by being allowed to freeze. For two periods of the year the working parties were entirely cut off from outside— while the snow fell most thickly, in November and December, and while it Climatic thawed in the early summer. Obstacles. T . During the winter proper it was possible to get a limited quantity of goods up from the sea on pack horses, which, following one behind another, trampled a narrow, hard track in the snow. Open-air work was continued as far into the autumn as the weather permitted. Then the majority of the navvies sought the low- lying districts, where work was still possible. Only sufficient remained behind to continue the tunnel work, which in th© Winter Work in the Tunnels. longer tunnels never ceased day or night until completion. As débris could not be removed beyond a tunnel’s mouth while the snow was still falling outside, the tunnel itself had to serve as dumping ground until after the thaw had begun. Consequently the force of men was so proportioned that the amount of material which they would be able to excavate should not unduly block the tunnel. In one of the longer bores the accumulations of a winter’s work would amount to several thousand cubic yards. When the time arrived for moving the débris the men proceeded to dig a tunnel through the snow. Sometimes this tunnel would have to be considerably over a quarter of a mile long, and its con- struction, even with continuous work, would occupy two or three weeks. So tightly was the snow packed in the drifts that dynamite