GR translation: winter and elastic light

[Mike Jing]

P5.4-14   But it is already light. How long has it been light? All
this while, light has come percolating in, along with the cold morning
air flowing now across his nipples: it has begun to reveal an
assortment of drunken wastrels, some in uniform and some not,
clutching empty or near-empty bottles, here draped over a chair, there
huddled into a cold fireplace, or sprawled on various divans,
un-Hoovered rugs and chaise longues down the different levels of the
enormous room, snoring and wheezing at many rhythms, in self-renewing
chorus, as London light, winter and elastic light, grows between the
faces of the mullioned windows, grows among the strata of last night’s
smoke still hung, fading, from the waxed beams of the ceiling.

What does it mean that the light is "elastic"?