Rotary Theory of Hail
The wind is supposed to rotate as in a cyclone, only the axis of the whirl is horizontal instead of vertical. Two horizontal layers of cloud exist-the upper layer of snow, the lower, or rain. The snowflakes, which form the nuclei of the hailstones, are caught in the whirl, are dipped in rapid succession into the two clouds, thus receiving alternate coatings of ice and snow, until at last they are hurried to the ground.
Edwin J. Houston, The Elements of Physical Geography, for the use of Schools, Academies, and Colleges. (Philadelphia: Eldredge & Brother, 1891) 107