Get out the microscope, because we’re going through this poem line-by-line.
Icicles filled the long window
With barbaric glass.
The shadow of the blackbird
Crossed it, to and fro.
Traced in the shadow
An indecipherable cause.
- Now we're back to winter again. Or maybe it's just a very cold autumn.
- These lines start out concrete and become hugely abstract. Stevens paints an image of icicles hanging from a window. The icicles look like glass, and you would expect to find glass in a window, but not this primitive or "barbaric" variety.
- Meanwhile, a blackbird flies back and forth in front of the window, casting its shadow on the ice.
- The shadow captures a certain "mood" – an atmosphere or emotion. You could read these lines as saying that the "mood" traced the "indecipherable cause" in the shadow, or that the mood, which is traced in the shadow, is an indecipherable cause. Tricky stuff, we know.
- An "indecipherable cause" is a cause that is hidden or unknown. Our best guess for what this means is that, if you didn't know that a blackbird was flying back and forth in the window, you wouldn't know what was causing the strange pattern of shadow.