His feet like unto fine brass - An emblem of his stability and permanence, brass being considered the most durable of all metallic substances or compounds.
The original word, χαλκολιβανον , means the famous aurichalcum , or factitious metal, which, according to Suidas, was ειδος ηλεκτρου, τιμιωτερον χρυσου , "a kind of amber, more precious than gold." It seems to have been a composition of gold, silver, and brass, and the same with the Corinthian brass, so highly famed and valued; for when Lucius Mummius took and burnt the city of Corinth, many statues of these three metals, being melted, had run together, and formed the composition already mentioned, and which was held in as high estimation as gold. See Pliny, Hist. Nat., lib. 34, c. 2; Florus, lib. 2, c. 16. It may however mean no more than copper melted with lapis calaminaris, which converts it into brass; and the flame that proceeds from the metal during this operation is one of the most intensely and unsufferably vivid that can be imagined. I have often seen several furnaces employed in this operation, and the flames bursting up through the earth (for these furnaces are under ground) always called to remembrance this description given by St. John: His feet of fine brass, as if they burned in a furnace; the propriety and accuracy of which none could doubt, and every one must feel who has viewed this most dazzling operation.
His voice as the sound of many waters - The same description we find in Ezekiel 43:2 ; : The glory of the God of Israel came from the way of the east; and his voice was like the noise of many waters: and the earth shined with his glory.