anches, they rolled the trunks
into the water. They placed these trunks side by side, with others,
laid transversely and pinned down, upon the top. Thus they formed
rafts, which they placed in a line across the stream, securing them
well to each other and to the banks. This made the foundation for the
bridge, and after this foundation was covered with other materials, so
as to make the upper surface a convenient roadway, the army were
conducted across it, and then a small detachment of soldiers were
stationed at each extremity of it as a guard.

Such a bridge as this answers a very good temporary purpose, and in
still water, as, for example, over narrow lakes or very sluggish
streams, where there is very little current, a floating structure of
this kind is sometimes built for permanent service. Such bridges will
not, however, stand on broad and rapid rivers liable to floods. The
pressure of the water alone, in such cases, would very much endanger
all the fastenings; and in cases where drift wood or ice is brought
down by the stream, the floating masses, not being able to pass under
the bridge, would accumulate above it, and would soon bear upon it
with so enormous a pressure that nothing could withstand its force.
The bridge would be broken away, and the whole accumulation--bridge,
drift-wood, and ice--would be borne irresistibly down the stream
together.

Scipio's bridge, however, answered very well for his purpose. His army
passed over it in safety. When Hannibal heard of this, he knew that
the battle was at hand. Hannibal was himself at this time about five
miles distant. While Scipio was at work upon the bridge, Hannibal was
employed, mainly, as he had been all the time since his descent from
the mountains, in the subjugation of the various petty nations and
tribes north of the Po. Some of them were well disposed to join his
standard. Others were allies of the Romans, and wished to remain so.
He made treaties and sent help to the former, and dispatched
detachments of troops to intimidate and subdue the latter. When,
however, he learned that Scipio had crossed the river, he ordered all
these detachments to come immediately in, and he began to prepare in
earnest for the contest that was impending.

He called together an assembly of his soldiers, and announced to them
finally that the battle was now nigh. He renewed the words of
encouragement that he had spoken before, and in addition to what he
then said, he now p