J. P. Hall— Short Cycle in Weather. 235 



of New York City, is another occasional cause of discrepancy 

 in the parallel. 



But the general uniformity of storm, tracks is conspicuous 

 enough in spite of these freaks to produce a strong resem- 

 blance between the temperature curves for the four stations 

 specified, and for intermediate ones ; and they will therefore 

 be found to exhibit much the same periodicity as is observed 

 in New York City. And since the same laws of storm move- 

 ment and wind direction prevail in Europe and Asia as in 

 America, and in the Southern as in the Northern Hemisphere, 

 subject to certain local modifications, it is probable that the 

 tendency of certain weather changes to recur at intervals of 

 27 days, observed in this country, may be found to exist in 

 corresponding latitudes elsewhere.* 



If, as seems to be the case, the immediate cause of warm 

 and cold waves is wind-direction, then the intensity of the 

 former must be proportional to the size and depth of the 

 barometric depressions, and to the breadth and height of such 

 anticyclones as happen to be adjacent thereto on the south. 

 The greater the neaping up of air in the latter and the 

 greater the rarefaction in the former, the steeper will be 

 the gradient between the two systems, and the wider and 

 stronger the sweep of the atmospheric currents. Examina- 

 tion of the daily weather maps for the three periods covered 

 by the temperature curves in Series I, II and III, ought to 

 show whether or not this is a sound conclusion. Such scrutiny 

 does, on the whole, warrant confidence in the existence of such 

 a relation. But the inquiry is more complicated than might 

 be supposed. Were all storms symmetrical or even similar in 

 shape and size, and were their routes always the same, and 

 were high pressure areas also alike in dimensions and move- 

 ment, the investigation would be very simple ; but such dif- 

 ferences exist among lows and among highs, and such are the 

 distortions of figure in instances, that the comparison does 

 not yield entirely harmonious results. One encounters occa- 

 sional anomalies. 



Thus the warm wave A in the first curve of Series I was 

 associated with a barometric depression whose center was mov- 

 ing eastward over Ontario on Aug. 21, 1889. This was the 

 most conspicuous low area that had crossed the country for ten 

 days, and it had no equal for nearly a fortnight afterwards. 

 The warm wave was correspondingly preeminent. This is a 



* Something of this sort, noted at Innsbruck and Paris by Nervander, and by- 

 Buys Ballot at Harlem, Danzig and Zwanenburg, is mentioned at page 80, in 

 "Die wichtigsten periodischen Erscheinungen," by Herman Fritz, of Zurich, who 

 himself contributes further data of the same kind on pages 396-8, exhibiting 

 a single or double oscillation in temperature at several other European stations, 

 four points in the Arctic regions and one in Africa. 



Am. Jour. Sci. — Third Series, Vol. XLV, No. 267.— March, 1893 

 17 



