. Bulletin - United States National Museum. Science. Figure 4.—Hoosac ["unnel. Bottom of the central shaft showing elevatoi car and rock skip: pumps ai far right. In the center, the iop bent li is being drilled by a single 1 olumn- mounted Burleigh drill. Mill mo lei si ale. Smithsonian photi 1 19260 N. has been extracted since at least 1000 Similar workings existed in the Tirol as early as about 1600 Two means of breaking away the rock are shown: to the left is the most primitive of all met he ids. the hammer and chisel, which require no Further description. At the right side,
. Bulletin - United States National Museum. Science. Figure 4.—Hoosac ["unnel. Bottom of the central shaft showing elevatoi car and rock skip: pumps ai far right. In the center, the iop bent li is being drilled by a single 1 olumn- mounted Burleigh drill. Mill mo lei si ale. Smithsonian photi 1 19260 N. has been extracted since at least 1000 Similar workings existed in the Tirol as early as about 1600 Two means of breaking away the rock are shown: to the left is the most primitive of all met he ids. the hammer and chisel, which require no Further description. At the right side, the two Figures are shown utilizing the first rock-breaking method in which a Force beyond that of human muscles was employed, the ane-old 'Tire-setting" method. The rock was thoroughly heated by a tierce lire built against ii- Face and then suddenly cooled by dashing water against it. Thethermal shock disintegrated the rock or ore into bits easily removable by hand. The practice of this method below ground, of course, produced a fearfully vitiated atmosphere. It is difficult to imagine whether the smoke, the steam, or the toxic fumes from the roasting ore was the more distressing to the miners. Even when performed by labor considered more or less expendable, the method could be employed only where there was ventilation ol Mime sort: natural chimneys and convection cur- rents were the clnd sources of air circulation. Despite the ol the fire system, its simplicity and efficacy weighed so heavily in its favor that us history ul use is unbroken almost to the present day. Fire setting was nt greatest importance during the years of intensive mining in Europe before the advent ol explosive blasting, but its use in many remote areas hardly slackened until the early 20th century because of its low cost when compared to powder. For this same reason, it did have limited application in actual tunnel work until about 1 Direct handwork with pick, chisel and hammer, and fire
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