The Sky

I saw a shadow on the ground
And heard a bluejay going by;
A shadow went across the ground,
And I looked up and saw the sky.
It hung up on the poplar tree,
But while I looked it did not stay;
It gave a tiny sort of jerk
And moved a little bit away.
And farther on and farther on
It moved and never seemed to stop.
I think it must be tied with chains
And something pulls it from the top.
It never has come down again,
And every time I look to see,
The sky is always slipping back
And getting far away from me.