The results thus made available exhibit the mean precipitation at each station of observation west of the Mississippi River for each month, for each season, and for the year. A number of other data are also tabulated, including the latitude, longitude, and altitude of each station, and the extent of each series of observations in years and months. In selecting material for the present purpose the shorter records were ignored. The variations from year to year are so great that an isolated record of a single year is of no value as an indication of the average rainfall. The mean of two or three years is almost equally liable to mislead, and only a long series of observations can afford accurate results. In the following tables no stations are included (with one exception) which show records of less than five years’ extent. Table I shows the precipitation of the Sub-humid Region; Table II, of the Arid Region; Table III, of the San Francisco Region; and Table IV, of the Region of the Lower Columbia. The limits of each region have been given in a former chapter, and need not be repeated. In each table the first column contains the names of the stations of observation; the second, their latitudes; the third, their longitudes (west from Greenwich); and the fourth, their altitudes in feet above the level of the sea. The next four columns show for each season of the year the mean observed rainfall in inches, and their sum appears in the following column as the mean yearly rainfall. In the last column the extent of each series of observations is given in years and months. In Table I the stations are arranged by latitudes, in Tables II, III, and IV, alphabetically. TABLE I.--_Precipitation of Sub-humid Region._