262 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 70 



ences the meteorological phenomena, but rather that variations in 

 this intensity of solar activity are of decisive influence for the 

 production of variations in the terrestrial phenomena. 



TWO-YEAR PERIODS IN THE SUN SPOTS AND IN THE TEMPERATURE 



OF SCANDINAVIA 



In the terrestrial magnetic elements there are found periods of six 

 months and of twelve months. These rest on the dififerent positions 

 of the earth in relation to the sun during its yearly movements. 

 Krogness has noted a very well-marked two-year period in the mag- 

 netic declination which may be ascribed to the accumulation of 

 three periods of six, eight, and twelve mo'nths. Since twenty-four 

 is a multiple of six, eight and twelve, the common action of these 

 three single periods must produce a two-year period. Woikof 

 and others have shown that a two-year period in meteorological 

 relations often appears. We see an indication of it in many of our 

 meteorlogical curves. It comes quite well into view in the tem- 

 perature curves V and VI of figure 96 and in part in the air pres- 

 sure curves figures 95, I, and 96, IV. But it is more important 

 that a similar two-year period also occurs in the curves of the sun 

 spots which are found in the same figures, curves III. If we take 

 into account only the smaller depressions of this curve we find them 

 very regularly each two years, namely in the years 1861, 1863, 

 1865, 1867, 1869. 1871, 1873, and 1875. In the year 1877 the depres- 

 sion in the curve III is lacking, but we find it in the curves V and 

 VI of figure 96 and also in curve I of figure 95. Depressions are 

 found also in the years 1879, 1881, 1882-3, 1884, 1886, 1888, 1890, 

 1892-3, 1894-5, 1897, 1899. Later, after 1901, it is more irregu- 

 lar. As a rule each second one of these minima is considerably 

 more marked than the one lying between. So for example very 

 marked m.inima occur in 1879, 1882-3, 1886, 1890, while the minima 

 lying between in the years 1881, 1884, and 1888 are less marked and 

 partly only slightly indicated. We, come in other words, to the 

 result that the curve of sun spots as well as the temperature curves 

 show rather well-marked two-years periods. 



Curv^e IV, figure 96, for the air pressure in Stockholm, shows, 

 for the sixty years, of its duration, in the years after 1865 a pretty 

 good direct agreement with the sun spot curve, and before 1865 with 

 the magnetic curve I. We will carefully compare this air pressure 

 curve for Stockholm and for a later time also curve V for Norway 

 with the curve of sun spots. We see then that in the year 1877 a 

 depression occurs in the temperature curves which is not found in 



