2 Chr. 26:15 And he [Uzziah] made in Jerusalem engines, invented by cunning men, to be on the towers and upon the bulwarks, to shoot arrows and great stones withal.
someone claimed that the "engines" such as described would not be invented for at least 400 more years; hence this passage is in error.
Research in credentialed sources, however, reveals two answers.
This option is offered by Herzog and Gichon in their excellent book, Battles of the Bible [249-51]. They see no reason why torsion-based siege engines used to throw arrows or stones could not have been invented earlier than is sometimes supposed: "With our growing appreciation of ancient Jewish dexterity in technical skills, one cannot deny that country -- because of its ever precarious security -- was forced to apply its inventiveness to military innovations."
They do acknowledge, however, that there would be no other evidence for this innovation. The reasoning is sound but without further support.
Commentaries by Dillard [210] and Myers [150], as well as Herzog and Gichon, note a study by Yadin which takes these engines to be not torsion-based, but rather "protective or shielding devices from which the defenders could shoot arrows and hurl stones." Herzog and Gichon describe Yadin's report of these as "wooden structures built on scaffolding that were added to the walls and towers so as to give additional height to the defences and gain extra space to marshal troops."
They note some drawbacks to such a setup (the wood could be set afire, though metal shields attached to it might repel fire-arrows; it would be hard to set up in time if an enemy came quickly), but Dillard notes that iconographic evidence in the form of murals depicting the siege of Lachsish, from a time shortly after Uzziah's, shows exactly such a device in use.
-JPH