+----------------------------+---------------------------------+ | | Percentage of annual rainfall. | | +---------------------------------+ | |Spring. | | | | |Summer. |Spring | | Station. | | |Autumn. | and | | | | | |Winter.|summer.| +----------------------------+-----+-----+-----+-------+-------+ | | | | | | | |Pembina, Dak. | 26 | 47 | 17 | 10 | 73 | |Fort Totten, Dak. | 31 | 44 | 15 | 10 | 75 | |Fort Abercrombie, Dak. | 26 | 46 | 18 | 10 | 72 | |Fort Wadsworth, Dak. | 29 | 42 | 17 | 12 | 71 | |Fort Sully, Dak. | 39 | 44 | 10 | 7 | 83 | |Sibley, Minn. | 21 | 40 | 29 | 10 | 61 | |Fort Randall, Dak. | 30 | 40 | 22 | 8 | 70 | |Fort McPherson, Nebr. | 36 | 40 | 17 | 7 | 76 | +----------------------------+-----+-----+-----+-------+-------+ |Fort Riley, Kans. | 22 | 43 | 24 | 11 | 65 | |Fort Hays, Kans. | 31 | 27 | 25 | 17 | 58 | |Fort Larned, Kans. | 24 | 45 | 23 | 8 | 69 | +----------------------------+-----+-----+-----+-------+-------+ |Fort Griffin, Tex. | 23 | 29 | 29 | 19 | 52 | |Fort Chadbourne, Tex. | 25 | 29 | 31 | 15 | 54 | |Fort McKavett, Tex. | 22 | 28 | 32 | 18 | 50 | |Fort Davis, Tex. | 11 | 51 | 28 | 10 | 62 | |Fort Clark, Tex. | 18 | 34 | 29 | 19 | 52 | |Fort Duncan, Tex. | 17 | 40 | 31 | 12 | 57 | |Fort McIntosh, Tex. | 18 | 38 | 31 | 13 | 56 | |Ringgold Barracks, Tex. | 19 | 36 | 32 | 13 | 55 | +----------------------------+-----+-----+-----+-------+-------+ The graduation of the ratios from north to south is apparent to inspection, but is somewhat irregular. The irregularity, however, is not greater than should be anticipated from the shortness of the terms of observation at the several stations, and it disappears when the stations are combined in natural groups. Dividing the whole series into three groups, as indicated by the cross lines in Table VII, and computing weighted means of the seasonal ratios, we have-- TABLE VII (_a_).[2] [2] In computing the several means of Table VII (_a_) from the seasonal means of Table VII, the latter were weighted according to the lengths of the records by which they had been obtained.