CHAPTER I 

 WEATHER AND CLIMATE 



THE BAROMETER AND THERMOMETER : PRESSURE AND 

 TEMPERATURE. The path having being prepared by simple 

 observations of this kind, a more careful study of the elementary 

 aspects of weather and climate may be begun. Hitherto, without 

 instruments and without precision, we have noted the frequent 

 variations in temperature, in the amount and the direction of 

 the wind, and in the humidity of the air, and our observations 

 have shown us that though there is some connection between these 

 different variables, the connection is not a very close one. We 

 have found that it is generally warmer in summer with an east 

 wind than with a west one, but colder in winter and spring ; that 

 our heaviest rains generally come with a westerly wind ; that an 

 east wind is at least sometimes a very dry wind, and so on. But 

 all these statements have only a generalised accuracy it may 

 rain heavily with an east wind, the air may be dry with a west 

 one, and so on. There is then probably some other element which 

 is affecting all the rest which we have not yet studied. 



This element is of course pressure, whose variations as measured 

 by the barometer tell us more about the probable course of the 

 weather than any direct observation we can make. As the 

 ordinary child is perfectly familiar with the appearance of a baro- 

 meter, and probably sees it consulted by some members of his 

 household daily, his attention should be directed to it at an early 

 age, and the opportunity may be taken to indicate the value to 

 mankind of instruments of precision. If in winter the glass is 

 high we have usually sunshine, often accompanied by considerable 

 cold or frost, and little wind ; if it is low, we have stormy or windy 

 and wet weather, probably with a higher temperature. In summer 

 the high glass means what we call " fine " weather ; the low, rain and 

 probably wind. Be content at first with simple generalisations 



