hundred and
thirty-five feet high and sixty feet broad. He strengthened it with hair
and rawhide so that it could withstand the blow of a stone weighing
three hundred and sixty pounds shot from a ballista; the machine itself
weighed three hundred and sixty thousand pounds. When Callias was asked
by the Rhodians to construct a machine to resist this helepolis, and to
bring it within the wall as he had promised, he said that it was
impossible.

5. For not all things are practicable on identical principles, but there
are some things which, when enlarged in imitation of small models, are
effective, others cannot have models, but are constructed independently
of them, while there are some which appear feasible in models, but when
they have begun to increase in size are impracticable, as we can observe
in the following instance. A half inch, inch, or inch and a half hole is
bored with an auger, but if we should wish, in the same manner, to bore
a hole a quarter of a foot in breadth, it is impracticable, while one of
half a foot or more seems not even conceivable.

6. So too, in some models it is seen how they appear practicable on the
smallest scale and likewise on a larger. And so the Rhodians, in the
same manner, deceived by the same reasoning, inflicted injury and insult
on Diognetus. Therefore, when they saw the enemy stubbornly hostile,
slavery threatening them because of the machine which had been built to
take the city, and that they must look forward to the destruction of
their state, they fell at the feet of Diognetus, begging him to come to
the aid of the fatherland. He at first refused.

7. But after free-born maidens and young men came with the priests to
implore him, he promised to do it on condition that if he took the
machine it should be his property. When these terms had been agreed
upon, he pierced the wall in the place where the machine was going to
approach it, and ordered all to bring forth from both public and private
sources all the water, excrement, and filth, and to pour it in front of
the wall through pipes projecting through this opening. After a great
amount of water, filth, and excrement had been poured out during the
night, on the next day the helepolis moving up, before it could reach
the wall, came to a stop in the swamp made by the moisture, and could
not be moved forwards, nor later even backwards. And so Demetrius, when
he saw that he had been baffled by the wisdom of Diognetus, withdrew