Today, King Hezekiah is a better engineer than we
thought. The University of Houston's College of
Engineering presents this series about the machines
that make our civilization run, and the people
whose ingenuity created them.
King David captured
Jerusalem in 1000 BC. That's why Jerusalem is
called "The City of David." But there's something
very odd about the way he did it. He called on a
volunteer to lead a group into the city through
some kind of underground tunnel. In the the Second
Book of Samuel, David says,
Whosoever getteth up to the gutter, and smiteth
the Jebusites ... he shall be chief and
It's that word gutter, or maybe it should be water
pipe, that we wonder about. You see, Jerusalem gets
its water from a source called Gihon Spring -- even
today. Gihon Spring lies outside the city and below
But there wasn't any tunnel for water in 1000 BC.
Three hundred years later, in 701 BC, King Hezekiah
cut a tunnel down to the Spring. He dug it to
supply water during an Assyrian siege. It says in
2nd Kings: "[Hezekiah] made a pool, and conduit,
and brought water into the city"
So how did David's man get into Jerusalem through a
tunnel that hadn't yet been built? That's one
problem. Archeological remains also raise a second
Hezekiah's tunnel is still there. And it's a crazy
piece of engineering. It lurches about, piercing
hard rock and missing softer stuff -- adding
needless excavation. Archeologists have made every
excuse for bad design. Hezekiah, after all, worked
under the stress of a siege.
An inscription adds to the problem. It tells how
workers tunneled from opposite directions:
On the day of the piercing through, the
stone-cutters struck through each to meet his
fellow, axe against axe. Then ran the water from
the spring to the pool for 1200 cubits, and a
hundred cubits was the height of the rock above the
head of the stone-cutters.
Now why would anyone in his right mind cut a
channel that high!
Israeli geologist Dan Gill looks at the tunnel in
its geological context. He sees what others missed.
This is terrain where you find Karst formations.
It's a limestone deposit, shot through with
Suddenly it all comes clear. David got into the
city through a series of limestone caves. Long
afterward, Hezekiah straightened out those caves.
He did some tunneling to connect with the Spring,
But he also used what was already there.
So we learn again not to underestimate our
forbears. Hezekiah built this old waterworks under
battle conditions. He followed the flow of the
land. He left a marvel of adaptive civil
engineering. And it's still there to see, 2700
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
Gill, D., Subterranean Waterworks of Biblical
Jerusalem: Adaptation of a Karst System.
Science, Vol. 254, 6 Dec. 1991, pp.
The Old Testament describes David's entry into
Jerusalem in 2 Samuel 5:8. Hezekiah's tunnel turns
up in 2 Kings 20:20; Isa. 22:9,11; 2 Chron. 32:2-4;
2 Chron. 32:30; Ben Sira (Ecclesiasticus) 48:17.
I am grateful to listener George Hollenback who
notes that out the hundred-cubit height of the
tunnel is a misreading of the Hebrew. Actually, it
refers to the depth of the tunnel -- a hundred
cubits was the distance from the tunnel ceiling to
the highest point above the tunnel
He quotes a later work by Dan Gill: How They Met:
Geology Solves the Mystery of Hezekiah's Tunnelers.
Archaeology Review, Vol. 20 No. 4
July/August 1994. This article shows a compressed
cross section through the straightened length of
the tunnel and, according to the scale shown, the
average height of the tunnel is about two meters,
with a maximum of about five meters near the Siloam
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.
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