312 ROCHESTER ACADEMY OF SCIENCE. [^lav 28, 



St. Lawrence gulf region to the north Atlantic they have sometimes 

 lingered on our Atlantic coast, and even retreated a short distance. 

 The reason seems to be that instead of the great area of low barometer 

 lying over the north Atlantic, as usual in winter, it has been lying 

 nearer our east coast, while a great "high" area has held over the 

 north Atlantic and western Europe. (Note the low which lingered 

 southland southeast of us for 8 days in April, (Apr, 19-26) and the 

 snow storms with severe cold in the Mediterranean cities during the 

 past winter). 



TEMPERATURE CHANGES; COLD WAVES. 



The cold waves following in the rear of cyclones are responsible 

 for the rapid falls of temperature experienced by the northern and 

 eastern parts of the United States. The extent or amplitude of these 

 changes depends chiefly upon the descent of the minimum tempera- 

 tures. The daily changes are least on the Pacific coast, and greatest 

 in the region of the upper Missouri. The midwinter daily changes 

 average 2 to 2. 5 degrees on the windward or Pacific coast ; 6 in Flor- 

 ida ; 8 over this region of the lakes ; and 9 to 10.5 degrees in Dakota 

 and Montana. 



The frequency and extent of the rapid falls of temperature are 

 greater over the upper great lakes. Falls amounting to 20 degrees in 

 24 hours are twice as frequent over the upper lakes as they are here, 

 and are four times as frequent here as they are over Florida, 



"The temperature changes here are remarkably small for a continental 

 climate, perhaps as small as for any place in the world so far from the ocean. 

 January and Februarj' are our worst months. During last January (1901) the 

 average daily range from highest day to lowest night temperature was only 14 

 degrees, and the average change of the daily mean temperature from day to day 

 was only 6 degrees. During February the similar range was less than 11 

 degrees and the daily change only 4 degrees. This is remarkable steadiness. 

 Only twice in thirty years has the daily range been as much as 50 degrees, and 

 both of these were rises. Once there was a range of 49 degrees, falling. The 

 figures for other places in comparison are not quickly available, but it is known 

 that the changes are generally much greater. At Boston, for example, the tem- 

 perature was once 70 degrees above zero at 10 a. m. and 4 degrees below at 

 midnight of the same day. This gives a range of 74 degrees in 14 hours. For 

 really changeable weather we may cite White River, Ont., about twenty 

 miles northeast of Lake Superior, where the following series of daily changes 

 are recorded : — 36 in A. m., -i-30 in p. m.; —42 the next a. m., +28 in p. M.; 

 — 28 the next A. M., and -I- 16 in the p. m. Many places along the northern 

 border of our own country experience ' weather ' of the same character. On 

 our east coast great changes occur suddenly because the ocean is warm and the 



