638 
dynamic. However, it is apparent that thermal hy- 
potheses are concerned with the laws governing the air in 
motion and that a thermal approach must not overlook 
the necessity of explaining the particular changes in the 
wind field which accompany pressure changes. Likewise 
dynamic hypotheses recognize the thermal origin of at- 
mospheric motion and a dynamic approach cannot disre- 
gard the observed temperature field. The ultimate goal 
of a complete explanation of pressure change involves 
the description of processes which satisfy all the laws 
governing the behavior of the atmosphere. In an at- 
tempt to advance toward this goal it may be con- 
venient to reason from one or more of the fundamental 
laws. Hence all approaches which have physical bases, 
whether they be called dynamic or thermal, supplement 
rather than compete with one another. The verified con- 
clusions of one approach should aid the extension of a 
different line of attack. 
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