Page:Popular Science Monthly Volume 35.djvu/299

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to Montreal, and, failing to make the connections necessary to reaching the northwest district, he "took to the spade" all summer long, except two days in the week which he devoted to botanizing. "In the autumn I shipped my collection of plants, and in two months had the mortification to learn that the vessel was totally wrecked in the St. Lawrence. During the next winter I did little, except employing myself with such skill as I was able in designing some flower-pieces, for which I got a trifle. Early the following spring I commenced labor again, and by the beginning of June had amassed about fifty dollars, which, with as much more borrowed from a friend, formed my stock of money for the next summer's tour. I started in the beginning of June from Montreal, and passing through Kingston went to New York [meaning the State, evidently], to which, after an excursion to Lake Simcoe, I returned; then visited the Falls of Niagara and Fort Erie, and crossed over to the United States, keeping along the eastern side of Lake Erie"; he crossed over to Pittsburg, back by way of Olean, Onondaga, and Sackett's Harbor to Montreal, and thence safely home to Scotland, "the plants I carried with myself being the whole that I saved out of the produce of nearly three years spent in botanical researches." Hard lines these and in those days for collecting botanists, which those who "stay at home at ease" do not appreciate. In the year 1824 he was commissioned to take charge of a cargo of living plants sent by the Edinburgh Botanic Garden to that of St. Petersburg. On his return he went into the nursery business in his native country. Then, with a laudable wish to better the prospects of his family, in 1844 he transported his home from the Scotch to the Canadian Ayr, in the province of Ontario, where he flourished and prospered for over thirty years of green old age, and died in the midst of numerous and prosperous children, grandchildren, and great-grandchildren.


Tornadoes.—Mr. J. P. Finley says that there are two principal conditions upon which the occurrence of tornadoes depends: one is a state of unstable equilibrium in the air, and the other a circulatory motion with reference to any center of disturbance. Tornadoes are most likely to occur in regions where warm moist air flows underneath a colder and drier stratum coming from another direction. Such regions are found in the Mississippi, Missouri, and Ohio Valleys, and in Alabama, Georgia, and the Carolinas. The summer season is the most favorable for tornadoes, when the interior of the continent is warmed up, and the air of the lower strata is drawn from lower latitudes far up into the northern portions of the country on the eastern side of the Rocky Mountains. If this unstable condition does not of itself induce a disturbance, one is readily brought about by the addition of any small effect from some other cause, as from extremely warm weather, in which the air strata close to the earth's surface become still hotter than those above them. Tornadoes very generally accompany an area of low barometer, and are to be looked for in the southeast quadrant only of the "low," at distances generally of from two hundred to five hundred miles from the center. But as the unstable state in a "low" very rarely extends down to the earth's surface, tornadoes are not necessarily visible in every general storm. The destructive violence of a tornado is sometimes confined to a path a few yards in width, or it may widen to the extreme limit of eighty rods. The tornado, with hardly an exception, occurs just after the hottest part of the day—most frequently between 3.30 and 5 p. m. The month of greatest frequency is May, April coming next. It is estimated that one hundred and forty-six tornadoes occur in the United States yearly. The vortex wind-velocities of the tornado-cloud vary from one hundred to five hundred miles an hour, from actual measurements. Velocities of from eight hundred to one thousand miles an hour are extremes that have been reported, but may not be altogether reliable. The cloud generated by the vortex assumes the form of a funnel, with the smaller end toward the earth. The characteristic effects of a tornado are objects drawn into the vortex from all sides, whirled upward and thrown outward by the circling air: structures are literally torn to pieces, as shown by the fineness of the débris; light objects are carried to great heights and also to great distances-? persons are stripped of clothing; fowls and birds are denuded of feathers and killed; trees are whipped to bare poles, uprooted or