in heavy haulage, so soon as fit roads can be had, belongs to the automobile, and its influence has already initiated a new era in American roadmaking.
Autumn Coloration (in plants). This phenomenon is associated with the deciduous habit, and is displayed by shrubs and trees throughout the temperate regions. The vivid colors have attracted a great deal of attention, but as yet no adequate explanation has been offered. The two types of color which appear, the reds and the yellows, seem to be due to different causes. The yellow is a post-mortem change of the green, an example of which may be observed in a poorly blanched stalk of celery, where the transition from green to white is seen to be through yellow. The red color is a product of the living substance of the leaves, manufactured at a time when the work of the leaf is beginning to flag. It has been suggested that the red color is of incidental advantage to the plant in that it raises the temperature of the leaves slightly and in this way protects the living substance from chill while it is retreating into the permanent parts of the plant previous to the fall of the leaves.
Auvergne (ō′vârn′y’), a branch of the Cevennes Mountains. The mountains lie in confused groups, sending up several summits to the height of 6,000 feet. Not only do the cone and domelike shapes of the summits betray a volcanic formation, but the great masses of peculiar rock that break through the crust of granite and gneiss render it evident that this was a great focus of volcanic action at a comparatively recent period. Among the summits that have apparently been at one time volcanoes, the most remarkable are Cantal, Mont-Dore and Puy-de-Dôme. All are now covered with verdure. There are rich deposits of iron, lead and other ores in the region, which was once an ancient province and today is a department of France.
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Aux′anom′eter. A device for measuring the growth of plants during short periods, when it is too slight readily to admit of direct measurement. In all forms the growth is magnified by causing the plant, acting on the short arm of a lever or the hub of a wheel, to displace an index five to twenty times more than the actual movement. (See figure.) In the more elaborate forms the index registers its movements on a smoked surface.
Av′alanche, a mass of snow or ice which slides down the sides of high mountains, often causing great destruction. There are various kinds of avalanches. Drift or powder avalanches are loose, dry snow, which is set in motion by the wind and rushes into valleys in the form of great dust-clouds. They usually occur in winter and are very dangerous, because of their suddenness, often suffocating men and animals and overturning houses by the compression of the air which they cause. Another kind of avalanche is like a landslide. The melting of the snow in spring makes the soil slippery, and great masses of snow are carried down the mountains by their own weight, taking trees and stones with them. If they come to a precipice in their course, as they often do, they are hurled with tremendous force into the valley beneath, destroying whatever is in their path. Ice avalanches often occur in summer. They are masses of ice which detach themselves from the mountain glaciers, commonly in July, August and September. Nine great Alpine avalanches, which destroyed 447 lives, are recorded between the years 1578 and 1827.
Avebury, Lord. See Lubbock, Sir John.
Averell, William Woods, American general and inventor, was born in Steuben County, New York state, November 5, 1832, and graduated from West Point in 1855. When the Civil War broke out, he was on duty in the west, fighting the Kiowa Indians. He then organized a corps of mounted riflemen, and in August, 1861, received the appointment of colonel, acting in most of the campaigns of the period with the Army of the Potomac and operating in cavalry raids. In 1865 he resigned, having the rank of major-general, and from 1866 to 1869 was United States consul-general in Canada, subsequently becoming interested in a large manufacturing company as president. While so occupied, he in 1869–70 discovered and perfected a process of obtaining cast steel direct from the ore; in 1879 he invented the American asphalt pavement; and subsequently he invented what is known as the Averell insulated conduit for electric wires and also a machine for laying electric conductors underground. He died in 1900.
Aver′nus, called now Lago d’Averno, is a small circular lake in Italy, It is about a mile and a half around, and lies in the crater of an extinct volcano. It is in some places 200 feet deep, and is almost completely shut in by steep and wooded heights. The sulphurous vapors arising from it were believed in ancient times to kill the birds that flew over it, and so it probably got its name from a Greek word meaning
