When they decided to build the Chunnel, the British and the French invited bids from reputed construction companies. While most of them quoted astronomical amounts for the job, two Sardarjis/Mallus/Biharis/Poles (take your pick) put a bid of $1000. Members of the Channel Tunnel Group called the two of them and asked for an explanation.
“I will dig from England and my brother from France”, one of them explained. “We meet at the center and the tunnel is complete”, the other completed.
“What if you don’t meet”, asked a naïve European.
The two entrepreneurs had thought about that. They looked at each other, smiled and replied.
“Then you get two tunnels.”
Hezekiah’s Tunnel, the longest tunnel built till the time without any intermediate shafts, was dug underneath Jerusalem in 701 BCE. This 1700 feet tunnel mentioned in the Bible was built during the reign of Hezekiah. From the Siloam inscription found on wall, we know that the tunnel was dug by two teams from opposite ends. The question is: how did they meet underneath? Why didn’t they create two tunnels?
This tunnel is not in a straight line. While a straight line would have produced a tunnel of 1050 feet, the architects took a convoluted route which added 700 extra feet. Still they managed to accurately meet and complete.
While many theories were proposed, including one which suggested that the tunnel diggers expanded a natural tunnel, they were all proved wrong. The latest issue of Biblical Archaeology Review has the answer.
The tunnelers were guided by communications from the surface, that is, by hammering on the bedrock above. Experiments conducted by Shimron and Frumkin demonstrated that communication by means of a hammer tapping on the bedrock above the tunnel could be an effective means of communication to a tunnel up to 50 feet below the surface and could be detected up to 80 feet. In short, “Acoustic messages between tunnel and surface must have been the dominant technique which controlled the complex proceeding underneath.” (Acoustic communication has been for centuries the method used for locating people trapped in mine catastrophes and earthquake collapses.)[Sound Proof]