province, owing to the comparatively high latitude, the variation in the number of hours of light and darkness each day during a year becomes conspicuous. In summer the sun is above the horizon from eighteen to twenty-four hours each day, and in winter the hours of darkness are correspondingly increased. The year is divided into but two seasons, summer and winter, the distinctive features of spring and fall, so well marked in the upper austral and transition provinces, disappearing. On account of the low mean annual temperature, and especially because of the shortness of the growing season, agriculture is of small importance. Along its southern border, more especially in southeastern Canada and Newfoundland, such small fruits as currants, huckleberries, raspberries, blackberries, cranberries, etc., grow wild and yield abundant returns when cultivated. In favoured localities white potatoes, turnips, beets, and certain varieties of the apple, as well as the more hardy cereals, are cultivated with moderate success. _The Arctic Province_ (Plate III) comprises the cold, treeless plains sloping to the Arctic Ocean and the summits of the higher mountains at the south which rise above the transition province. The one controlling climatic feature is the low temperature, the mean for each year being 32 deg. F. or lower. The winters are longer and more severe than in the boreal province, and the summers short and hot. Insolation, on account of the length of the days in summer of the main area of the province and the free exposure on the mountain summits to the southward, is intense, but its beneficial effect on vegetation is largely counterbalanced by the influence of the lingering snow and ice. In the mountainous regions of North America the arctic province is the birthplace of numerous glaciers. Although destitute of trees, the arctic, or arctic-alpine province, as it may be termed, is rendered glorious in numberless localities by the profusion and brilliancy of its flowering annuals. SECONDARY DISTURBANCES OF THE ATMOSPHERE In the broad, general movements of the atmosphere over North America embraced in what are termed the planetary and continental winds there are many disturbances due to more or less local changes in conditions, the most conspicuous of which are whirlwinds, chinook winds, thunder-storms, tornadoes, cyclones, and hurricanes. While some of these disturbances are local, as the whirlwind and tornadoes, and may not extend beyond the boundaries of the particular climatic provinces where they originate, others, as the cyclones and hurricanes, may affect the climate of several provinces.