der. For
these woods are weak and easily catch fire. Over the boardings let there
be placed wattles very closely woven of thin twigs as fresh as possible.
Let the entire machine be covered with rawhide sewed together double and
stuffed with seaweed or straw soaked in vinegar. In this way the blows
of ballistae and the force of fires will be repelled by them.

CHAPTER XV

HEGETOR'S TORTOISE

[Illustration: HEGETOR'S RAM AND TORTOISE

1. From a MS. of the sixteenth century (Wescher's Poliorcetique des
Grecs).

2. From a model made by A. A. Howard.]

1. There is also another kind of tortoise, which has all the other
details as described above except the rafters, but it has round it a
parapet and battlements of boards, and eaves sloping downwards, and
is covered with boards and hides firmly fastened in place. Above this
let clay kneaded with hair be spread to such a thickness that fire
cannot injure the machine. These machines can, if need be, have eight
wheels, should it be necessary to modify them with reference to the
nature of the ground. Tortoises, however, which are intended for
excavating, termed in Greek [Greek: oryktides], have all the other
details as described above, but their fronts are constructed like the
angles of triangles, in order that when missiles are shot against them
from a wall, they may receive the blows not squarely in front, but
glancing from the sides, and those excavating within may be protected
without danger.

2. It does not seem to me out of place to set forth the principles on
which Hegetor of Byzantium constructed a tortoise. The length of its
base was sixty-three feet, the breadth forty-two. The corner posts, four
in number, which were set upon this framework, were made of two timbers
each, and were thirty-six feet high, a foot and a quarter thick, and a
foot and a half broad. The base had eight wheels by means of which it
was moved about. The height of these wheels was six and three quarters
feet, their thickness three feet. Thus constructed of three pieces of
wood, united by alternate opposite dovetails and bound together by
cold-drawn iron plates, they revolved in the trees or amaxopodes.

3. Likewise, on the plane of the crossbeams above the base, were erected
posts eighteen feet high, three quarters of a foot broad, two thirds of
a foot thick, and a foot and three quarters apart; above these, framed
beams, a foot broad and three quarters of a foot thick, held the whol