ostinato

That penetrating ray of contemplation is always suspended near something because of greatness of wonder, yet it operates neither always nor uniformly in the same mode. For that vitality of understanding in the soul of a contemplative at one time goes out and comes back with marvelous quickness, at another time bends itself, as it were, into a circle, and yet at another time gathers itself together, as it were, on one place and fixes itself, as it were, motionless. Certainly if we consider this rightly, we see the form of this thing daily in the birds of the sky. Now you may see some raising themselves up on high; now others plunging themselves into lower regions and often repeating the same manner of their ascent and descent. You may see some turning to the side, now to the right, now to the left, and while coming down a little ahead now in this part, now in that, or advancing themselves almost not at all, repeating many times with great constancy the same changes of their movements.

-- Richard of St. Victor The Mystical Ark
Translated by Grover A. Zinn