lacking somewhat in rainfall; but this want can be easily supplied by utilizing the living streams; and, further, these streams will afford fertilizing materials of great value. The Humid Region of the lower Columbia and the Sub-humid Region of the Great Plains have been thus briefly indicated in order that the great Arid Region, which is the subject of this paper, may be more clearly defined. THE ARID REGION. The Arid Region is the great Rocky Mountain Region of the United States, and it embraces something more than four-tenths of the whole country, excluding Alaska. In all this region the mean annual rainfall is insufficient for agriculture, but in certain seasons some localities, now here, now there, receive more than their average supply. Under such conditions crops will mature without irrigation. As such seasons are more or less infrequent even in the more favored localities, and as the agriculturist cannot determine in advance when such seasons may occur, the opportunities afforded by excessive rainfall cannot be improved. In central and northern California an unequal distribution of rainfall through the seasons affects agricultural interests favorably. A “rainy season” is here found, and the chief precipitation occurs in the months of December-April. The climate, tempered by mild winds from the broad expanse of Pacific waters, is genial, and certain crops are raised by sowing the seeds immediately before or during the “rainy season”, and the watering which they receive causes the grains to mature so that fairly remunerative crops are produced. But here again the lands are subject to the droughts of abnormal seasons. As many of these lands can be irrigated, the farmers of the country are resorting more and more to the streams, and soon all the living waters of this region will be brought into requisition. In the tables of a subsequent chapter this will be called the San Francisco Region. Again in eastern Washington and Oregon, and perhaps in northern Idaho, agriculture is practiced to a limited extent without irrigation. The conditions of climate by which this is rendered possible are not yet fully understood. The precipitation of moisture on the mountains is greater than on the lowlands, but the hills and mesas adjacent to the great masses of mountains receive a little of the supply condensed by the mountains themselves, and it will probably be found that limited localities in Montana, and even in Wyoming, will be favored by this condition to an extent sufficient to warrant agricultural operations independent of irrigation. These lands, however, are usually supplied with living streams, and their irrigation can be readily effected, and to secure greater certainty and greater yield of crops irrigation will be practiced in such places. IRRIGABLE LANDS.