Ancient tunnels
Already common by the 8th century bc in Iran, was a single-ended tunnel, known as a qanat, which tapped an underground aquifer and brought water to the surface for irrigation. Such tunnels were constructed by the ‘shaft method’, i.e. by a series of vertically sunk shafts, the bottoms of which were linked together by short headings underground. Because several work-faces could be opened simultaneously, this was a relatively expeditious method of construction. From Iran, the technology spread to Egypt and was put to service in the oases of its deserts. It came into the Greek world either through the Sa mians, mentioned by Herodotus (III. 26), who lived and worked in Egypt; or directly from Persia, either brought by Greeks who worked there, or communicated through agents of the king, Cambyses II, with whom Polycrates was in alliance.
   This ‘shaft method’, used in the qanats, can be seen, applied here on Samos , in the last stretch of tunnel close to the surface, which brings the water from the spring at Aghiades to the north entrance of the main tunnel. Perhaps the most notable example of the technique, however, is the 7km tunnel sup plying Athens with water, and built only a couple of decades after the tunnel of Eupalinos; there are other examples at Syracuse and at Lake Copais in Boeotia, where the work was never completed. But the much more complex, double-ended tunnel, employed where the ‘shaft method’ cannot be applied because the depth of ground is too great, is rarer and slow er—because it permits only two simultaneous work faces. The earliest example is the tunnel on Samos ; but, at 1,036m, it is not the longest. An emissary tunnel, 1,600m long, was dug to drain Lake Nemi near Rome at the turn of the 5th century bc; and another, 1,400m long, to drain Lake Albano nearby, begun in 397 bc. In both these Italian examples, the volcanic rock was easier to cut and the depth of the tunnel underground, marginally less: but the achievement is no less astounding for that.
   The technology was probably brought to the Italian peninsula by the Greeks or through the agency of Carthaginians from Egypt and North Africa, and it was widely applied, first by the Etruscans and later by the Romans. Although no trace of it has been uncovered, the longest tunnel ever undertaken in Antiquity would appear to have been that which carried the Anio Novus to Rome from the Simbruini hills: it could not have been much less than 2,250m long. A curiosity among Roman double-ended tunnels is that constructed by Nonius Datus at Saldae, in Algeria, which though much shorter and shallower than Eupalinos’s, failed to meet in the centre, and required complex machinations to retrieve the situation.
   The first written, comprehensive source that we possess on the instruments and methods of surveying in Antiquity—although it does not talk about tunnel construction as such—is the 1st century ad work, On the Dioptra, by Hero of Alexandria, in which he discusses his design for what is the predecessor of the modern theodolite.

Samos Island is part of the Northern Aegean Island Group, Greece.

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