TOfnD, 99 



one at the high- and another at the low-pres- 

 sure area. If the difference between the read- 

 ings of the two barometers is very great, and 

 the areas are comparatively close together, we 

 may expect the change to be sudden and vio- 

 lent. 



" High " and " low " as applied to a barom- 

 eter are only relative terms. There is no fixed 

 point on the index of the instrument that can 

 be said to be arbitrarily high or low. For this 

 reason a single barometer is not of much use. 

 If it begins to fall from any point, and falls 

 rapidly, it indicates that an area of a much 

 lower pressure is approaching. The same is 

 true of a high-pressure area, if the barometer 

 rises rapidly from any point. 



If we study the air motions in these systems 

 sufficiently to get at least an inkling of the 

 law of their movements, it becomes a very 

 interesting subject. 



Wind from whatever cause serves a wonder- 

 fully useful purpose in the economy of nature. 

 Without wind, heat and moisture could not be 

 distributed over the face of the earth and our 

 globe would not be a fit habitation for man. 

 How wonderful is the machinery of Nature, 

 that can first forge a world into shape and 

 afterward decorate it with green grass and 

 flowers that are watered by the "early and 

 latter rain"! 



