Posted on 04/03/2009 4:45:40 PM PDT by raybbr
One of the greatest engineering achievements of ancient times is a water tunnel, 1,036 meters (4,000 feet) long, excavated through a mountain on the Greek island of Samos in the sixth century B.C. It was dug through solid limestone by two separate teams advancing in a straight line from both ends, using only picks, hammers, and chisels. This was a prodigious feat of manual labor. The intellectual feat of determining the direction of tunneling was equally impressive. How did they do this? No one knows for sure, because no written records exist. When the tunnel was dug, the Greeks had no magnetic compass, no surveying instruments, no topographic maps, nor even much written mathematics at their disposal. Euclid’s Elements, the first major compendium of ancient mathematics, was written some 200 years later.
There are, however, some convincing explanations, the oldest of which is based on a theoretical method devised by Hero of Alexandria five centuries after the tunnel was completed. It calls for a series of right-angled traverses around the mountain beginning at one entrance of the proposed tunnel and ending at the other, maintaining a constant elevation, as suggested by the diagram below left. By measuring the net distance traveled in each of two perpendicular directions, the lengths of two legs of a right triangle are determined, and the hypotenuse of the triangle is the proposed line of the tunnel. By laying out smaller similar right triangles at each entrance, markers can be used by each crew to determine the direction for tunneling. Later in this article I will apply Hero’s method to the terrain on Samos.
Hero of Alexandria’s theoretical method for working out the line of a tunnel dug simultaneously from both ends.
Hero’s plan was widely accepted for nearly 2,000 years as the method used on Samos until two British historians of science visited the site in 1958, saw that the terrain would have made this method unfeasible, and suggested an alternative of their own. In 1993, I visited Samos myself to investigate the pros and cons of these two methods for a Project MATHEMATICS! video program, and realized that the engineering problem actually consists of two parts. First, two entry points have to be determined at the same elevation above sea level; and second, the direction for tunneling between these points must be established. I will describe possible solutions for each part; but first, some historical background.
Samos, just off the coast of Turkey in the Aegean Sea, is the eighth largest Greek island, with an area of less than 200 square miles. Separated from Asia Minor by the narrow Strait of Mycale, it is a colorful island with lush vegetation, beautiful bays and beaches, and an abundance of good spring water. Samos flourished in the sixth century B.C. during the reign of the tyrant Polycrates (570–522 B.C.), whose court attracted poets, artists, musicians, philosophers, and mathematicians from all over the Greek world. His capital city, also named Samos, was situated on the slopes of a mountain, later called Mount Castro, dominating a natural harbor and the narrow strip of sea between Samos and Asia Minor. The historian Herodotus, who lived in Samos in 457 B.C., described it as the most famous city of its time. Today, the site is partly occupied by the seaside village of Pythagorion, named in honor of Pythagoras, the mathematician and philosopher who was born on Samos around 572 B.C. Pythagoras spent little of his adult life in Samos, and there is no reason to believe that he played a role in designing the tunnel.
Polycrates had a stranglehold on all coastal trade passing through the Strait of Mycale, and by 525 B.C., he was master of the eastern Aegean. His city was made virtually impregnable by a ring of fortifications that rose over the top of the 900-foot Mount Castro. The massive walls had an overall length of 3.9 miles and are among the best-preserved in Greece. To protect his ships from the southeast wind, Polycrates built a huge breakwater to form an artificial harbor. To honor Hera, queen of the Olympian gods, he constructed a magnificent temple that was supported by 150 columns, each more than 20 meters tall. And to provide his city with a secure water supply, he carved a tunnel, more than one kilometer long, two meters wide, and two meters high, straight through the heart of Mount Castro.
Delivering fresh water to growing populations has been an ongoing problem since ancient times. There was a copious spring at a hamlet, now known as Agiades, in a fertile valley northwest of the city, but access to this was blocked by Mount Castro. Water could have been brought around the mountain by an aqueduct, as the Romans were to do centuries later from a different source, but, aware of the dangers of having a watercourse exposed to an enemy for even part of its length, Polycrates ordered a delivery system that was to be completely subterranean. He employed a remarkable Greek engineer, Eupalinos of Megara, who designed an ingenious system. The water was brought from its source at Agiades to the northern mouth of the tunnel by an underground conduit that followed an 850-meter sinuous course along the contours of the valley, passing under three creek beds en route. Once inside the tunnel, whose floor was level, the water flowed in a sloping rectangular channel excavated along the eastern edge of the floor. The water channel then left the tunnel a few meters north of the southern entrance and headed east in an underground conduit leading to the ancient city. As with the northern conduit, regular inspection shafts trace its path.
Continues......
I saw your post about the 100 meter tunnel in Rome. I thought this might interest your ping list.
Ping, sir.
Samos, Samos!
I'm sure my History of Ancient Greece prof is rolling over in his grave! He was born and grew up on Lemnos, (not Lesbos he would emphasize) before coming to the US to finish his studies and then terroize the students in Dev of Western Civ!
/rimshot!
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Thanks raybbr and ConservativeMind! |
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interesting
Hezekiah's Tunnel, or the Siloam Tunnel is a tunnel that was dug underneath the Ophel in Jerusalem about 701 BC during the reign of Hezekiah. It was probably a widening of a pre-existing cave and is mentioned in the Bible.
The tunnel[1], leading from[2] the Gihon Spring to[3] the Pool of Siloam, was designed to act as an aqueduct to provide Jerusalem with water during an impending siege by the Assyrians, led by Sennacherib. The curving tunnel is 533m long, and by using a 30 cm (0.6%) gradient altitude difference between each end, conveyed water along its length from the spring to the pool.
According to an inscription (the Siloam inscription) found within it, the tunnel was excavated by two teams, one starting at each end of the tunnel and then meeting in the middle.
Source:
http://en.wikipedia.org/wiki/Hezekiah's_Tunnel
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