38

ENGINEERING

& SCIENCE NO . 1



This picture was tak en inside the tunnel looking tow ard

the southern entrance. Although the floor is mor e or less

lev el along the whole length, the roof slopes in line with

the rock strata. Metal grillwork no w cov ers the

wa ter channel on the left to pre vent hapless tourists

from falling in; the photo on the next page sho ws how

treacher ous it was before.

The cre w digging into the

norther n mountainside

started off perfectly in line

with the southern crew ,

but later zigzagged off

course, perhaps to b ypass

areas of unstab le rock.

They did, howe ver , meet up

almost perfectly with the

southern tunnel, albeit at

right angles. Right: At the

southern end, the water

channel is a staggering

nine meters lo wer than the

floor of the tunnel.

A visit to the tunnel today reveals its full

magnificence. Except for some minor irregulari-

ties, the southern half is remarkably straight.

The craftsmanship is truly impressive, both for

its precision and its high quality . The tunnel’ s

two-meter height and width allowed workers

carrying rubble to pass those returning for more.

The ceiling and walls are naked rock that gives

the appearance of having been peeled off in layers.

W ater drips through the ceiling in many places

and trickles down the walls, leaving a glossy ,

translucent coating of calcium carbonate, but some

of the original chisel marks are still visible. The

floor is remarkably level, which indicates that

Eupalinos took great care to make sure the two

entrances were at the same elevation above sea level.

Of course, a level tunnel cannot be used to

deliver a useful supply of water . The water itself

was carried in a sloping, rectangular channel

excavated adjacent to the tunnel floor along its

eastern edge. Carving this inner

channel with hand labor in solid

rock was another incredible

achievement, considering the

fact that the walls of the channel

are barely wide enough for one

person to stand in. Y et they are

carved with great care, maintain-

ing a constant width throughout.

At the northern end, the bottom

of the channel is about three

meters lower than the tunnel

floor , and it gradually slopes

down to more than nine meters

lower at the southern end. The

bottom of the channel was lined

with open-topped rectangular

clay gutters like those in the

drawing on page 34.

No matter how it was planned, the tunnel

excavation itself was a remarkable accomplish-

ment. Did the two crews meet as planned? Not

quite. If the diggers had kept faith in geometry

and continued along the straight-line paths on

which they started, they would have made a

nearly perfect juncture. The path from the north,

however , deviates from a straight line. When the

northern crew was nearly halfway to the junction

point, they started to zigzag as shown in the

diagram on the left, changing directions several

times before finally making a sharp left turn to

the junction point. Why did they change course?

No one knows for sure. Perhaps to avoid the

possibility of digging two parallel shafts. If one

shaft zigzagged while the other continued in a

straight line, intersection would be more likely .

Or they may have detoured around places where

water seeped in, or around pockets of soft material

that would not support the ceiling. In the final

stretch, when the two crews were near enough

to begin hearing each other , both crews changed

direction as needed and came together . The sharp

turns and the difference in floor levels at the junction

prove conclusively that the tunnel was excavated

from both ends. At the junction itself, the floor

level drops 60 centimeters from north to south,

a discrepancy of less than one-eighth of a percent

of the distance excavated. This represents an

engineering achievement of the first magnitude.

No one knows exactly how long it took to

complete the project, but estimates range from 8

to 15 years. W orking conditions during excava-

tion must have been extremely unpleasant. Dust

from rubble, and smoke from oil lamps used for

illumination, would have presented serious

ventilation problems, especially when the workers

had advanced a considerable distance from each

entrance.