Amid the infinite variety of their nomenclature (which changed several times in the course of the centuries) these machines might be reduced to two systems:  some acted like slings, and the rest like bows.

The first, which were the catapults, was composed of a square frame with two vertical uprights and a horizontal bar.  In its anterior portion was a cylinder, furnished with cables, which held back a great beam bearing a spoon for the reception of projectiles; its base was caught in a skein of twisted thread, and when the ropes were let go it sprang up and struck against the bar, which, checking it with a shock, multiplied its power.

The second presented a more complicated mechanism.  A cross-bar had its centre fixed on a little pillar, and from this point of junction there branched off at right angles a short of channel; two caps containing twists of horse-hair stood at the extremities of the cross-bar; two small beams were fastened to them to hold the extremities of a rope which was brought to the bottom of the channel upon a tablet of bronze.  This metal plate was released by a spring, and sliding in grooves impelled the arrows.

The catapults were likewise called onagers, after the wild asses which fling up stones with their feet, and the ballistas scorpions, on account of a hook which stood upon the tablet, and being lowered by a blow of the fist, released the spring.

Their construction required learned calculations; the wood selected had to be of the hardest substance, and their gearing all of brass; they were stretched with levers, tackle-blocks, capstans or tympanums; the direction of the shooting was changed by means of strong pivots; they were moved forward on cylinders, and the most considerable of them, which were brought piece by piece, were set up in front of the enemy.

Spendius arranged three great catapults opposite the three principle angles; he placed a ram before every gate, a ballista before every tower, while carroballistas were to move about in the rear.  But it was necessary to protect them against the fire thrown by the besieged, and first of all to fill up the trench which separated them from the walls.

They pushed forward galleries formed of hurdles of green reeds, and oaken semicircles like enormous shields gliding on three wheels; the workers were sheltered in little huts covered with raw hides and stuffed with wrack; the catapults and ballistas were protected by rope curtains which had been steeped in vinegar to render them incombustible.  The women and children went to procure stones on the strand, and gathered earth with their hands and brought it to the soldiers.

The Carthaginians also made preparations.

Hamilcar had speedily reassured them by declaring that there was enough water left in the cisterns for one hundred and twenty-three days.  This assertion, together with his presence, and above all that of the zaimph among them, gave them good hopes.  Carthage recovered from its dejection; those who were not of Chanaanitish origin were carried away by the passion of the rest.