A simple extension and application of the principles learned through the preceding exercises make it possible for us to forecast coming weather changes in a general way. These suggestions are, however, not at all to be considered as a complete discussion of this complicated problem. Weather forecasts include the probable changes in _temperature_, _wind direction_ and _velocity_, and _weather_. Pressure is not included. Begin your practice in weather forecasting by considering only the changes that may be expected at your own point of observation, and at first confine yourself to predicting temperature changes alone. =Temperature.=——Provide yourself with a blank weather map. Draw an isotherm east and west across the map, through your station. Draw a few other isotherms all the way across the map, parallel with the first one, and so arranged that they will be equal distances apart, the most northerly one running through northern Maine and the Northwestern States, and the most southerly one through southern Florida and Texas. Recalling what you have already discovered concerning the eastward movement of our weather conditions, what forecast will you make as to the coming temperatures at your station? Add some additional east and west isotherms, so that there will be twice as many on your map as before. What effect will this change in the temperature distribution on your map have upon the temperature forecast you make for your station? Formulate a general rule as to temperature forecasts under the conditions of isothermal arrangement here suggested. On a second blank weather map draw an isotherm through your station inclined from northwest to southeast. Draw a few other isotherms parallel to the first, and each one representing a temperature 10° higher than that indicated by the adjacent isotherm on the east. Make a general forecast of the temperature conditions that may be expected at your station, as to _kind of change_, if any; _amount of change_, and _rapidity of change_. Of the isotherms just drawn, erase every second one; still, however, letting those that are left represent differences of temperature of 10°. What forecast will you now make as to temperature? How does this forecast compare with that just made? Now draw twice as many isotherms on your map as you had in the first place, still letting these lines represent differences of temperature of 10° in each case. Make a forecast of the kind, amount, and rapidity of temperature change at your station under the conditions represented on this map. How does this forecast compare with the two just made? Formulate a general rule governing temperature forecasts in cases of isothermal arrangement such as those here considered.