"one august event..."See in text(Text of the Poem)
The adjective “august” means impressive, awesome, or inspiring of respect or reverence. Hardy characterizes the tragic “event” of the Titanic’s impact with the iceberg as being one that will be remembered and honored for many years to come.
The adjective “opulent” means excessively luxurious or rich. Hardy creates a jarring contrast between the grandeur of the Titanic’s high-status passengers and image of the ship’s wreckage at the bottom of the ocean.
The verb “to thrid” is an archaic spelling for “to thread,” which means to flow through something, as in a ship thridding / threading a current. Hardy contrasts the epic fires of the first two lines of this stanza with the sonic imagery of “cold currents” of water threading through the steel chambers as though they were playing an instrument.
A “pyre” is a pile of combustible material that is usually used to burn a dead body during a funeral. Hardy’s use of the word refers to both the fires that would have heated the ship from within its steel chambers and the funerals of so many people after the tragedy.