Dylan hasn’t rhymed the word “glass” in over three decades.  When he last did it was in reference to that snake that he mysteriously does not name at the end of “Man Gave Names To All The Animals“:

He saw an animal as smooth as glass
Slithering his way through the grass
Saw him disappear by a tree near a lake . . .

The “glass“/”grass” last rhyme of the song is the last time Dylan will be responsible for the rhyming–he leaves us to come up with “snake” from the rhyme with “lake.”

Clever.

We have to name him from the sound Dylan gives us, but he won’t say it/sing it . . . a rather snake in the grass move.  The -s sound helps, too, though; can you hear the snake slithering with all those onomatopoeic s’s?  We may not be able to see him, disappearing at all by that tree, but we can hear him and we can identify him, so ingrained as he is into our psyche.

Just  a little help, Dylan seems to be saying, is all we need to point out the snake though we can’t see it.

Here is is singing it in 1981 in London, June 30th, when he was smack dab in the middle of his gospel stage: