The blues of the sky provide the mood, and more than a handful of birds--magpies, curlews, hummingbirds, jackdaws--are sent into the open spaces that Heffernan, a tranquil, philosophical poet who sees the universe with the help of ""the inmost eye in the middle of me,"" stirs up in this, his fourth collection, winner of the 1993 Iowa Poetry Award. Showing a spare, musical touch combined with a masterful sense of color, the most captivating poems explore the nature of things, the unchartered places where objects intersect or connect, especially where the human gives way to the divine, as in ""A