were disintegrated and fell off under the action of the water. The
Romans being good chemists knew the effect of vinegar on lime, therefore
when they encountered calcareous rock instead of water they used vinegar
which very readily split up and disintegrated this kind of obstruction.
The work of tunneling was very severe on the laborers, but the Romans
did not care, for nearly all the workmen were slaves and regarded in
no better light than so many cattle. One of the most notable tunnels
constructed by the old Romans was that between Naples and Pozzuoli
through the Posilipo Hills. It was excavated through volcanic tufa and
was 3,000 feet long, 25 feet wide, and of the pointed arch style. The
longest of the Roman tunnels, 3-1/2 miles, was built to drain Lake
Fucino. It was driven through calcareous rock and is said to have cost
the labor of 30,000 men for 11 years.

Only hand labor was employed by the ancient people in their tunnel
work. In soft ground the tools used were picks, shovels and scoops,
but for rock work they had a greater variety. The ancient Egyptians
besides the hammer, chisel and wedges had tube drills and saws provided
with cutting edges of corundum or other hard gritty material.

For centuries there was no progress in the art of tunneling. On the
contrary there was a decline from the earlier construction until late
in the 17th century when gunpowder came into use as an explosive in
blasting rock. The first application of gunpowder was probably at
Malpas, France, 1679-1681, in the construction of the tunnel on the
line of the Languedoc Canal 510 feet long, 22 feet wide and 29 feet
high.

It was not until the beginning of the nineteenth century that the art
of tunnel construction, through sand, wet ground or under rivers was