32 



Introduction to the Study of Science 



they reach Montana, where they swing directly east or some- 

 what south of east and cross the country. A few develop in 

 the central Rocky Mountain region ; and a very small number, 

 formed in the vicinity of Hudson Bay, move south through 

 Manitoba and then eastward over the Great Lakes. Trace 

 the paths of several anticyclones across the continent. Com- 

 pare with these the paths of cyclones. Are they the same? 

 What kinds of weather accompany anticyclones? Are they 

 always accompanied by fair weather ? 



Observation of the behavior of anticyclones or high-pressure 

 areas suggests that there are two varieties : one supplying the 

 adjacent lows with descending and outflowing air, which is 

 cold and dry; the other remaining practically inactive for 

 many days over a particular locality, or moving so slowly that 

 it may require weeks in crossing the continent. In these anti- 

 cyclonic areas, winds may circulate around the outer isobars, 

 but there is little or no evidence of descending air in the central 

 region. 



Weather observations should be made daily by each student, prefer- 

 ably morning and evening. The following items should be observed 

 and recorded in convenient form, with a column for results of com- 

 parison with the United States Weather Maps. Test also the gen- 

 eral weather features of cyclonic areas, which have been described 

 above. 



A useful form is as follows : 



NAME OF OBSERVER 



A graphical representation of the daily pressure and temperature 

 may be made to illustrate clearly the changes. Such a diagram should 

 extend uninterruptedly over one or more weeks. 



