To stare inside, or retrospection,
A star inside a rectangle, a recollection:
This hollow square could easily have been there.
--The childish snow-forts, built in flashier winters,
Could have reached these proportions and been houses;
The mighty snow-forts, four, five, stories high,
Withstanding spring as sand-forts do the tide,
Their walls, their shape, could not dissolve and die,
Only be overlapping in a strong chain, turned to stone,
And grayed and yellowed now like these.
Where is the ammunition, the piled-up balls
With the star-splintered hearts of ice?
This sky is no carrier-warrior-pigeon
Escaping endless intersecting circles.
It is a dead one, or the sky from which a dead one fell.
The urns have caught his ashes or his feathers.
When did the star dissolve, or was it captured
“Carrier-warrior-pigeon” is a reference to the pigeons that were used to transport information during wartime before radio was used. She is revisiting the pigeon with a “dead wing with damp feathers” from the first stanza. 
 “Escaping endless intersecting circles” may be in reference to the circles within Paris streets that she mentioned in the first stanza, or the acrobatic movements of war planes to avoid being shot down. 

Paris 7 A.M.