Page:Popular Science Monthly Volume 25.djvu/731

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since 1755 when December and January were warmer than the mean. The warm seasons come at irregular intervals, and do not suggest any law; seventeen of them came between 1755 and 1821, and seventeen between 1821 and 1884. In seventy-six per cent of these exceptional winters, the month of November also was warmer than usual. Herr Hellman asserts that the chances are eighty-one to nineteen that a warm February will follow a warm December and January, and fifty-seven to forty-three that the same will be the case with March. Thus, the chance is that a winter that begins by putting on a mild face in November will preserve the same aspect all through. In regard to the seasons following these exceptional winters, Herr Hellman finds that a moderately mild winter is more frequently followed by a cold spring, and a very warm winter more usually by a warm spring; and, in general, that the warmer the winter the warmer will be the ensuing spring. These conclusions contradict popular notions.

Physiographic Conditions of Minnesota.—In a lecture on the "Physiographic Conditions of Minnesota Agriculture," recently delivered before the State Horticultural Society, Professor C. W. Hall claimed for that State a nearly central position on the North American Continent, as fixed by lines drawn from Eastport to Astoria, and from Behring Strait to the Isthmus of Panama. Of its area, 83,365 square miles, 78,600 square miles are land, while the rest of the territory is occupied by some 8,000 or 10,000 lakes; 48,000 square miles are forest, and 31,000 prairie. Not quite 40,000 square miles are drained into Hudson Bay, and 7,689 square miles into the St. Lawrence, while the rest of the area of the State sheds its water into the Mississippi. The height of the land ranges from 602 feet above the sea, at Lake Superior, to 2,400 feet in the highest part of the Mesabi, or dividing range between the water-sheds, and averages, for the whole State, perhaps about 1,200 feet. Much of Minnesota is covered by the drift, the various constituents of which—granites and schists, sandstones, clays, and limestones—have been ground up and mingled in utter confusion, so that the land is adapted to the greatest diversity of crops. The average annual rainfall is about 28-27 inches, or about three quarters of an inch less than the average for the whole United States, excluding Alaska. The average January temperature is nearly 12° Fahr., while the July average is nearly 71° Fahr; and the difference between the warmest summer day and the coldest winter night is about 120° Fahr. A reduction in the average temperature is observed of one degree for every 350 feet of additional elevation. As in Nebraska, a gradual increase in rainfall appears to be taking place as more of the prairie-soil is brought under the plow; and the streams are becoming larger, and springs are flowing where once water could not be obtained.

An Absolute Unit of Light.—An absolute standard for the measurement of the intensity of light has long been wanting. All the standards heretofore proposed are imperfect, because in none of them has it been possible to secure complete uniformity in intensity and color. A satisfactory standard should be identical at all times and in all places; should be of convenient size; and should be white enough to be comparable with all modern lights in every region of the spectrum. These conditions appear to be fulfilled in the standard proposed by M. Violle in 1881, which, after some improvement in processes, has been definitely adopted by the International Congress of Electricians. It is the light emitted by a square centimetre of melted platinum at the temperature of solidification (1,775° C, or 3,227° Fahr.). This light nearly resembles the incandescent electric light, and is constant during the whole process of solidification. Its value, expressed in one of the old standards, is 1 carcel 1/2·08 of the Violle unit.

Birds' Tastes for Color and Music.—Mr. E. E. Fish has published in the "Bulletin" of the Buffalo Naturalists' Field-Club a paper on "The Intelligence of Birds," in which he ascribes to birds a keen perception of color and capacity to be gratified by artistic arrangements of colors, and a strong susceptibility to musical melodies. Evidence of the enjoyment of color is given by the tasteful combinations with which many birds