J. P. Hall — Short Cycle in Weather. 



233 



and 11th. That these are intimately related appears from this 

 fact : Such phases of the weather are associated with winds 

 from lower latitudes, bringing warm air upon the scene ; these 

 southeasterly, southerly or southwesterly winds constituting 

 part of a system always to be found about a region of low 

 barometric pressure and prevailing on the eastern or southern 

 sides of such depressions. When, therefore, one of these areas 

 approaches a place from the west, and is passing, with its center 

 north of the station, these warm winds dominate ; and when 

 the depression has gone far enough to the eastward to permit 

 the northwesterly and northerly winds of its western half to 

 sweep over the spot, air from higher and colder latitudes is 

 transported thither, and the temperature falls. These latter 

 winds are also characteristic of the front of a high pressure 

 system, such as usually follows the low area ; and a study of 

 these alternate "lows" and "highs" is the foundation of mod- 

 ern meteorology. A map showing the distribution offair s pres- 



sure on the morning of Aug. 7, 1891, is submitted, and the 

 positions successively occupied by its center from the 3d to the 

 10th indicated thereon. It will thus be seen that Utah came 

 under the fullest influence of the warm winds of this system 

 on Aug. 4, St. Paul on the 8th, and New York on the 10th. 

 Its effect at the last named place and at St. Louis seems to have 

 been heightened by the passage of a similar area from Mani- 

 toba to the St. Lawrence Valley on Aug. 9-11. The high 



