This is the Hour of Lead –
It is interesting to note that lead is considered a stable element, with a half life of 1017 years. With this in mind, this phrase can mean that a tragedy that took an hour to occur could last for a seemingly infinite time in the mind of the observer. Through this juxtaposition, she means to show that pain is timeless—both to all people throughout history, and everlasting in the memory of each individual who has ever experienced it.
There is also the obvious interpretation that Lead is dark and heavy, and that an hour of remembering is obviously very painful and heavy in the heart of the narrator.
(credit to: http://www.galleries.com/Lead)
Lead also is a metal which causes poisoning— people were aware of its toxicity as early as two thousand years ago. (And we’re still putting it in paint? Right…)
During the civil war, bullets were also made of lead. This is an hour that can kill you.
To help improve the meaning of these lyrics, visit "After great pain a formal feeling comes (J341, F372)" by Emily Dickinson and leave a comment on the lyrics box