The valleys amid the Pacific mountains, which fall in the upper austral province, are in general low at the north in reference to sea-level, and become higher and higher at the south. For example, the upper austral region in central Washington is but 400 or 500 feet above the sea, while in Mexico it lies in general at an altitude of between 4,000 and 6,000 feet. The upper austral province may be termed warm temperate, with a marked contrast between the heat of summer and the cold of winter. The summers are long, with an average temperature of 70 deg. or 75 deg., while the winters are variable, with frequent cold periods when ice forms and snow-storms are not rare. The snow seldom remains on the ground for more than a few days at a time, however, except in the northeast, where the warm temperate climatic conditions of the province under review merge with those of the colder region to the northward embraced in the transition province. The upper, like the lower austral, presents two well-marked divisions in reference to humidity--an eastern or humid and a western or semihumid portion; the dividing line is in the neighbourhood of the one hundredth meridian. In the eastern division the mean annual precipitation in the Piedmont region to the east of the Appalachians and on the coastal plain adjacent to the Atlantic in Maryland and New Jersey is from 40 to 80 inches, but decreases westward, and on the border of the Great plateaus in Kansas and Nebraska is about 20 inches. In the western division the annual precipitation is less than 20 inches, and agriculture without irrigation is uncertain and usually impossible. To the east of the one hundredth meridian the rain is somewhat evenly distributed throughout the year, although an increasing dryness of the summer is easily detected as one travels from east to west, but in the various upper austral valleys of the Pacific mountain region the precipitation is mostly during the winter, and the summers are practically rainless. The marked difference in precipitation between the humid and semihumid division of the upper austral province is recorded on the surface of the land by the vegetation. In the eastern division the entire region, with the exception of the prairies in the central part of the Mississippi basin, was originally clothed with a varied and beautiful forest, consisting mainly of broad-leaved trees, such as the hickory, maple, oak, etc., while the semihumid western division is treeless, except in immediate proximity to streams.