METEOROLOGY REVOLUTIONIZED BY THE WEATHER-MAP. 41 



■ciple. In the topography of the country we have the hill and valley. Although 

 these combinations form only two factors the diversity of landscape which they 

 produce is infinite. 



The atmospheric counterpart of the hill and valley is high and low barom- 

 eter — technically called " High" and " Low." These terms the reader should 

 bear in mind. "Barometer" is a long word, so in the phraseology of the 

 Weather-Bureau it is dropped, and the words " High" and " Low " respectively 

 stand for high and low barometer. 



The terrestrial hill and valley are quite permanent — as a mass they may be said 

 to be permanent. The mountain chains and hills and the valleys remain about as 

 they were when man first inhabited the earth ; but not so with the atmospheric 

 hill and valley. They are ever changing ; never twice alike. They are as varied 

 as the clouds, and in their variety they more resemble the kaleidoscope than any. 

 thing else. These changes, from hour to hour, day to day, produce what we 

 term " the weather." They are ever on the move, on general lines, from the 

 west towards the east. We live on a globe ; the heat which sustains life thereon 

 comes from the Sun, but this heat alone will not sustain life. The body that 

 receives the benefit of this heat must be in condition to appropriate it to a good 

 advantage. Satellites have not this power or quality — planets have. Through the 

 Weather-Map we are enabled to understand the important part heat plays in the 

 economy of Nature as never before. From the old system we learned about 

 the seasons and their general cause, but before the advent of the Map it was 

 impossible to explain these peculiar lines of heat and cold which are independent 

 of latitude and of the position of the sun in the ecliptic. We could not explain 

 why the isothermal lines at times run from the extreme northeast to the southwest, 

 or from the southeast to the northwest. Why it was sometimes as warm in New 

 England as in the cotton States. Why cold in New England while it was very 

 warm in the region of Dakota and Montana. Why some localities at times suffer 

 from drouth while others are abundantly supplied with moisture. 



Under the old system they even did not know what a storm was; they had 

 no conception of storm centres and where one storm began and another ended. 



If it rained two or three weeks in succession it was thought to be one pro- 

 tracted storm, while on the contrary it was the result of a series of storm centres 

 passing over the country. Neither could the old system explain the tornado, 

 hurricane, or cyclone, call it what we will. It could not satisfactorily explain 

 numerous phenomena connected with this department of nature — all for the 

 simple reason that the facts which the Weather-Map has revealed to us were then 

 inaccessable. If we will heed the teachings of this wonderful instrument, which 

 may well be termed "The Geography of the Atmosphere," we will understand 

 this department of Nature as never before. 



The Map reveals the fact that the areas of high and low barometer are al 

 the while passing over the earth's surface, in belts and on general lines, from the 

 west towards the east. From this it must not be understood that they move on 

 parallels of latitude, nor even take quite straight courses across the country, for 



