Geometry of a hawk's flight

One of the poets featured in the current Poetic Likeness Exhibit -- featuring photographs and paintings and sculptures of poets along with a few favorite lines -- at the National Portrait Gallery is Robert Penn Warren (1905-1989).   Although I hugely admire Warren's novel, All the King's Men, I am not very familiar with Warren as a poet.  The gallery posted, beside Warren's photo, a few lines about a hawk.  And I went searching online to find more.  The exhibit's quote was from Warren's "Mortal Limit" but my search led first to "Evening Hawk" -- with a first stanza bright with geometry;  I offer that stanza here.

It Crossed My Mind

     In Elinor Gordon Blair --  my English teacher during my junior and senior years at Indiana Joint High School in Indiana, Pennsylvania -- I found a woman who became a life-long inspiration to me.  An insatiable reader and always curious, Elinor Blair seemed to learn from every thing that came along. Such an excellent strategy  -- and I learned it from her.  
     Mrs Blair -- is my habit to continue to call her by this formal name -- still lives in Indiana and she is 99 years old.  Three years ago she published a poetry collection, It Crossed My Mind.  These following stanzas from Blair's collection use imagery from geometry to describe the destructive way in which "skeletons of steel" have remade our American landscapes. 
     Thank you, Mrs. Blair, for these lines and for the ways you have enriched my life.