|Fort Stevens, Oreg |17.67| 7.88|18.21| 34.81| 78.57| 6 5| |Fort Umpqua, Oreg |16.83| 2.86|15.64| 32.08| 67.41| 5 10| |Fort Vancouver, Wash | 8.70| 3.78| 9.17| 16.72| 38.37| 16 11| |Fort Yamhill, Oreg |13.10| 2.39|13.20| 26.90| 55.59| 9 3| |Portland, Oreg |13.75| 2.50|11.31| 19.64| 47.20| 7 0| |Port Townsend, Wash | 5.45| 4.22| 2.31| 4.07| 16.05| 5 6| |San Juan Island, Wash | 5.01| 4.60| 7.89| 10.84| 28.34| 9 4| +----------------------------+-----+-----+ ----+------+------+-------+ DISTRIBUTION OF RAIN THROUGH THE YEAR. In a general way the limit of agriculture without irrigation, or “dry farming”, is indicated by the curve of 20 inches rainfall, and where the rainfall is equally distributed through the year this limitation is without exception. But in certain districts the rainfall is concentrated in certain months so as to produce a “rainy season”, and wherever the temperature of the rainy season is adapted to the raising of crops it is found that “dry farming” can be carried on with less than 20 inches of annual rain. There are two such districts upon the borders of the Arid Region, and within its limits there may be a third. _First District._--Along the eastern border of the Arid Region a contrast has been observed between the results obtained at the north and at the south. In Texas 20 inches of rain are not sufficient for agriculture, while in Dakota and Minnesota a less amount is sufficient. The explanation is clearly developed by a comparison of the tables of rainfall with reference to the distribution of rain in different seasons. TABLE V.--_Precipitation of Texas._