NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC 1 55 



Briickner actually found that in Siberia and south Russia in 

 periods otherwise warm and dry, particularly 1856-65, the winter 

 was abnormally cold, the summer abnormally hot. However he 

 remarks that south Russia and Siberia are distinguished by a peculiar 

 march of temperature. The variations there march partly reversed 

 from other regions. He is of the opinion that these irregularities 

 " find their explanation by the great cold of their winter." 



Briickner raises the interesting point that the temperature ampli- 

 tude of his thirty-five year period seems to be less in the tropics 

 than in higher latitudes, while the amplitude of the eleven-year 

 period of Koppen is afifected in the opposite direction. 



After Briickner, William Lockyer, in 190 1, considering the mag- 

 netic epochs, and the variation in the length of the sun spot period 

 itself, worked out the period of the frequency of sun spots to be 

 about 35.4 years. The time between minimum and maximum 

 varies regularly in a cycle of about 35 years. Bigelow (1902) found 

 in dififerent ways a period of about thirty-five years in the variations 

 of the sun spots and the magnetic horizontal intensity (see also J. 

 Rekstad, 1908, pi. i). Schuster, in 1905, derived a period of sun 

 spots of 33.375 years. Besides he finds also shorter periods of 

 13.57, 1 1. 125, 8.38, 5.625, 4.81, 3.78 and 2.69 years. 



F. G. Hahn (1877) undertook investigations on the separate 

 year seasons of meteorological elements of the several yearly sea- 

 sons separately and connected their variations with those of the solar 

 spots. He found, as a general rule, that the temperature varies 

 oppositely as the sun spots, although this was not equally marked 

 in all times of the year. 



By considering the daily maximum temperatures in summer in 

 Geneva for five sun spot periods after 1843, MacDowall (1896) 

 found that " in sun spot maximum years a greater number as well 

 of very hot as of very cold days occurs than in sun spot minimum 

 years." He would explain this by the consideration that the sun's 

 radiation has greater intensity at sun spot maximum than at mini- 

 mum. Thus a greater number of very hot days at maximum should 

 be expected, but it may be the cause also of greater evaporation and 

 cloud building which may call forth very cold days. MacDowall 

 has also given curves for the June temperature in Trieste, Paris, 

 Aix la Chappelle. and Bremen for the years 1831 to 1893, and these 

 show much correspondence with the inverted sun spot curves, par- 

 ticularly after i860, with amplitudes between maxima and minima 

 from 1.5° to 2° C. His five-year smoothed August curves for 



