The poem seems to indicate that Urania, slumbering, is not yet aware of the death of Adonais.
He dozed, and it seemed to him that all the world was slumbering.
And they talked about it nearly the whole night, slumbering only a few hours.
It was a signal that awakened all the slumbering passions of a nation.
There was confidence to be got from a mere look at that slumbering Jovian form.
And with a cry of delight he ran towards the slumbering Portly.
Undetected by a single human witness, without interruption from slumbering master or lazy hind, the total deed was done.
He had been there for hours watching his slumbering comrade.
The day dawned quietly, and shed a sort of still, holy light over the slumbering man.
Of a certainty Gloy was not slumbering, and Gloy was not there!
mid-14c. alteration of slumeren (mid-13c.), frequentative form of slumen "to doze," probably from Old English sluma "light sleep" (cf. Middle Dutch slumen, Dutch sluimeren, German schlummern "to slumber"). Frequentative on the notion of "intermittent light sleep." For the -b-, cf. number, lumber, chamber, etc. Related: Slumbered; slumbering.
mid-14c., from slumber (v.). Slumber party first recorded 1942. Slumberland is from 1875.