Teacher's Leaflet. 1 145 



(10). Look at the third map and compare the three maps. Where do 

 the high and low centers seem to have originated? How long does it 

 take a high or low to cross the United States ? How far north and south 

 does a high or low with all its isobars extend? 



(11). What do the dotted lines on your map mean? Do they follow 

 exactly the isobars? 



(12). What is the greatest isotherm on your map? Through or near 

 what towns does it pass? 



(13). Do the regions of high air pressure have the highest temperature 

 or the lowest? Do high temperatures accompany low pressures? Why? 



(14). What is the condition of the sky just east of a low center? 

 What is its condition just west of low? 



(15). If the isobars are near together in a low it means that the wind 

 is moving rather fast and that there will be a well-marked storm. Look 

 at the column giving wind velocity. Was the wind blowing toward the 

 center of the low on the map? If so, does that mean it is coming fast 

 or slow? How does this fact correspond with the indications shown by 

 the distance between the isobars? 



(16). Describe the weather accompanying the approach and passage 

 of a low in the region where your town is situated. What sort of clouds 

 would you have, what winds, what changes of the barometer and ther- 

 mometer ? 



Lesson XVII. 



HOW TO FIND THE GENERAL DIRECTION AND AVERAGE RATE OF MOTION 



OF HIGHS AND LOWS. 



Observations: 



(i). On the first map of the series of three given you put an X in 

 red pencil or crayon at the center of the high and a blue one at the center 

 of the low ; or if you do not have the colored pencils, use some other 

 distinguishing marks for the two. If there are two highs and two lows 

 use a different mark for each one. 



(2). Mark the position of each center on the map for the following 

 day with the same mark that you first used for that area. Do this for 

 each of the highs and lows until it leaves the map or until your maps 

 have been used. All the marks of one kind can be joined by a line, using 

 a red line for the red marks and a blue line for the blue marks. 



(3). What do you find to be the general direction of the movement 

 of the highs and lows? 



