"Just the same way," the Forecaster answered, "except that they're all sent in cipher, of course. Once in a while the cipher results in some queer combinations. The regular routine requires that an observer send the temperature, the barometric pressure of the atmosphere, the amount of rain or snow, the direction and force of the wind, the state of the weather, the types of clouds and the highest and lowest temperature since the last observation. I remember once, while at the Milwaukee station, we got the following message from La Crosse, Wisconsin: "'Cross All My Ink Frozen' "It so happened that we had Charlie Cross working at that station at that time, but the message did not apply to him, nor, for that matter, to his ink. On second consideration and reading, the message read very differently. 'Cross' was the code name of the station; 'All' meant that his barometer read 30.02 and that his morning temperature was zero; 'My' conveyed the information that his sky was clear, the wind from the south and that his minimum temperature for the night was zero; 'Ink' informed us that the wind velocity at the station was six miles an hour and that he could not add the usual height of the water in the Mississippi as the river was 'frozen.' Similar code messages are sent in twice a day from each of the two hundred stations. "So you see, Mr. Tighe, if all these various observations combine to describe a certain weather type, if we can check up the accuracy by comparison with stations to the north, south, east and west, and if all these combine to produce a certain definite picture, our weather forecast can be made with tolerable certainty. As an absolute matter of fact, during the past six years, the exact percentage of accurate forecasts is eighty-two per cent, and of the eighteen per cent remaining, eleven were partly right. That leaves a very small proportion of mistakes in weather forecasting. Now, let us take in detail the cold wave which Fred, quite rightly, said was on its way here. "Here is the Weather Map of the day before yesterday." He placed it on the table in front of the old farmer. "You will notice two sets of curved lines, solid lines and dotted lines. The solid lines are called 'isobars' and they follow the course of places which have the same barometric pressure. The dotted lines are called 'isotherms' and they follow the lines of places having the same temperature. These maps are never twice the same. The Weather Bureau does not possess on its books the record of any two days when the weather was duplicated over the United States." "You mean that every day's weather map is different?" "As different as every human face," the Forecaster replied, "and to those of us who have done much forecasting, it is as easy to see from the map when the weather is going to be peaceful or stormy as it is to tell whether a man is smiling or scowling. But let us look at these three charts closely, and you will see just why Fred was right.