I will … make the crooked places straight; rather, I will make the rugged places level. No doubt intended generally, "I will smooth his way before him." The gates of brass … the bars of iron. According to Herodotus, the gates of Babylon were of solid bronze, and one hundred in number (1.
179). Solid bronze gates have, however, nowhere been found, and would have been inconvenient from their enormous weight. It is probable that the "gates of brass," or "bronze," whereof we read, were always, like these found at Ballarat, of wood plated with bronze.
To the eye these would be "gates of bronze." Gates of towns were, as a matter of course, secured by bars, which would commonly be made of iron, as the strongest material. Iron was well known to the Babylonians (Herod; 1:186).