Transactions and proceedings and report of the Philosophical Society of Adelaide, South Australia . ent—thewhirlwind—it is directly upwards, but in a more or less oblique direction,on account of the forward motion of the whole and the friction with thesurrounding air. Generally the gyrations of the svhirlwind cease as suddenly as theybegin—first in the centre, then at the circumference. A dust column,seen at a distance, appears invariably to break off at some distance abovethe ground, the objects comprising the lower part rapidly descending,while those in the upper portion seem slowly to float
Transactions and proceedings and report of the Philosophical Society of Adelaide, South Australia . ent—thewhirlwind—it is directly upwards, but in a more or less oblique direction,on account of the forward motion of the whole and the friction with thesurrounding air. Generally the gyrations of the svhirlwind cease as suddenly as theybegin—first in the centre, then at the circumference. A dust column,seen at a distance, appears invariably to break off at some distance abovethe ground, the objects comprising the lower part rapidly descending,while those in the upper portion seem slowly to float upwards, con-spicuous articles of small weight being often carried to considerable dis-tances ; the light dust preserves its columnar form sometimes for aquarter of an hour or more without apparently changing its place. In conclusion, the following is a short resume of what is intendedto be shown in the foregoing, viz :— I. Whirlwinds are upward currents of heated air, endowed witha spiral motion at th^* circumference, progressive motion and smalldiameter in proportion to their
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1878
