I 4 o GENERAL SCIENCE 



their capacity for moisture increases, and clouds disappear as result 

 of the vaporization of the water particles forming the clouds. 



The paths traversed by the centres of these areas of low pressure on 

 their eastward journeys across country generally range farther north 

 in summer, and much to the southward in winter. This results in 

 weather changes far more varied than would be true if dependent only 

 upon the approach of storm areas from the west and their passing on 

 eastward. 



The isotherms on weather maps connect places reporting the same 

 temperatures. Isobars connect places having the same atmospheric 

 pressure as shown by barometer readings. 



So numerous are variations from the general rules of weather that 

 no brief summarization of weather conditions is at all adequate. Local 

 conditions are often large factors in the weather of any particular sec- 

 tion. "As fickle as the weather" does not, however, signify that the 

 great controlling causes of the weather may not in a general way be 

 understood by those who have made no extended study of Meteorology. 



Exercises 



1. What distinction is made in the use of the terms weather and climate? 



2. What besides total annual amount is important in the relation of rainfall 

 to the raising of crops? 



3. What geographic conditions make winds from the north and northwest in 

 the interior of this continent of lower humidity? 



4. Name several ways in which men protect themselves from unfavorable 

 weather conditions. 



6. Contrast the exposure incident to occupations and travel now and in 

 earlier generations. 



6. To what extent can man control the weather? 



7. Explain the clearing of the sky and the cooler weather when a low moves 

 on eastward, and northwesterly winds spring up. 



8. In what ways do winds affect the well-being of mankind ? 



9. Trace any apparent relationship between climate and the civilization of 

 any people. 



THE THERMOMETER, AND HEAT TRANSMISSION 



Changes in the volume of a body by reason of its being 

 heated or cooled are proportional to the changes in its'tem- 



