4 8 



and distances to the right of OYto denote their corre- 

 sponding dates. What is the technical expression for a 

 curve formed in this way ? 



Interpretation of Isotherms and Isobars 



From a map of the world, showing the isotherms, deter- 

 mine what regions have a mean temperature of about 50, 

 60, and 70. What is the mean temperature of your own 

 city ? 



From a map of the world showing the isobars determine 

 what regions have approximately the same mean baromet- 



180 160 140 120 100 80 60 4O 20 O 20 



FIG. 34. Isothermal lines. 



ric pressure. Maps for the purpose will be furnished by 

 the teacher. 



From a local newspaper, cut out the weather chart (Fig. 

 35) for the day and pin it in your laboratory notebook. 

 What meaning does this weather chart have for you ? 

 Write a brief account of the information which it contains 

 relative to distance and local weather conditions. 



