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.

"At eight o'clock in the morning, the day before yesterday, there was a
well-defined 'low' with a barometer of 29.8 just east of Salt Lake City,
driving warmer weather before it. Issaquena County was just recovering
from the effects of a 'high,' which, as you can see on the map, was
disappearing by its favorite route, the St. Lawrence Valley. What was
your temperature here the day before yesterday, Anton?"

"Thirty-six degrees, sir," the crippled lad answered, rapidly consulting
his week's record, which was hanging on the wall.

"Fairly cold, you see. And the wind, Tom?"

Tom pulled out a note-book from his pocket.

"North-east, sir," he said.

"Very good. Now, Mr. Tighe, you can see from the map that the barometric
pressure, the isobar, running through this part of the country shows a
barometric pressure of 30.30. From what Anton told you, it is easy to
see that, the day before yesterday, Issaquena County was still in the
grip of the ta