What does it mean to move with silver feet?

While reading Oscar Wilde's, The Picture of Dorian Gray, I came across this:

There was a silence. The evening darkened in the room. Noiselessly and with silver feet the shadows crept in from the garden. The colours faded wearily out of things.

I tried searching for what it meant to move with silver feet but found only discussions of Bush having a silver foot in his mouth. On this site I found mentions of clay feet, but nothing of silver feet.

Move with silver feet is most likely a reference to quicksilver, which is another name for the liquid metal mercury. So, it's the movement of shadows being described here.

Quicksilver -- ODO

(noun) 1.1 Used in similes and metaphors to describe something that moves or changes very quickly, or that is difficult to hold or contain.

His mood changed like quicksilver
The achievement is palpable: the quicksilver movements of fish, the movement of water and the play of light through it, the interior of a whale's mouth.