Note return — FOOTNOTES

A still more recent theory is that of Busse36 who considers the mechanical action of the wind a very important factor. He observed: (a) Frost splits sometimes occur at higher temperatures than 14°F. (b) Most splits take place shortly before sunrise, i.e., at the time of lowest air and soil temperature; they are never heard to take place at noon, afternoon, or evening. (c) They always occur between two roots or between the collars of two roots, (d) They are most frequent in old, stout-rooted, broad-crowned trees; in younger stands it is always the stoutest members that are found with frost splits, while in quite young stands they are altogether absent, (e) Trees on wet sites are most liable to splits, due to difference in wood structure, just as difference in wood structure makes different species vary in this regard. (f) Frost splits are most numerous less than three feet above the ground.