Therefore, the first model of the sequence, reflecting elemental
rock-breaking techniques, depicts a hard-rock copper mine (fig. 1).
Due to the absence of specific information about such works during the
pre-Christian eras, this model is based on no particular period or
locale, but represents in a general way, a mine in the Rio Tinto area
of Spain where copper has been extracted since at least 1000 B.C.
Similar workings existed in the Tirol as early as about 1600 B.C. Two
means of breaking away the rock are shown: to the left is the most
primitive of all methods, 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 age-old "fire-setting" method. The
rock was thoroughly heated by a fierce fire built against its face and
then suddenly cooled by dashing water against it. The thermal shock
disintegrated the rock or ore into bits easily removable by hand.
[Illustration: Figure 4.--HOOSAC TUNNEL. Bottom of the central shaft
showing elevator car and rock skip; pumps at far right. In the center,
the top bench is being drilled by a single column-mounted Burleigh
drill. MHT model--1/2" scale. (Smithsonian photo 49260-N.)]
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 of some sort: natural chimneys and
convection currents were the chief sources of air circulation. Despite
the drawbacks of the fire system, its simplicity and efficacy weighed
so heavily in its favor that its history of use is unbroken almost to
the present day. Fire setting was of greatest importance during the
years of intensive mining in Europe before the advent of 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 1900.
Direct handwork with pick, chisel and hammer, and fire setting were
the principal means of rock removal for centuries. Although various
wedging systems were also in favor in some situations, their
importance was so slight that they were not shown in the model.