NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC I77 



(1903), and others. P. Schreiber (1896, 1903) found a probable 

 eleven-year period in the precipitation at different stations in Europe, 

 but with two maxima, one, two years after sun spot maximum, 

 the other at the time of sun spot minimum, and with two minima, 

 one coincident with sun spot maximum and the other three years 

 after the sun spot minimum. 



A. Buchan (1903) found a double period in the precipitation in 

 Great Britain, so that a minimum occurs shortly after sun spot 

 minimum and another shortly after sun spot maximum. The first 

 and weaker maximum is much less marked in Scotland and west 

 Europe than in southeast England where the principal maximum 

 occurs nearer the sun spot maximum. 



G. Hellmann (1909) has investigated the relation of variation of 

 precipitation in different parts of Europe to the sun spot period 

 and finds that there is no universally followed rule about it. In 

 most cases of the stations examined by him there occur within a sun 

 spot period two maxima of rainfall which occur about six or five 

 years from one another. At the time of sun spot minimum there oc- 

 curs at most stations a maximum of rainfall, but in consequence of 

 the progress of wet and dry years from south toward north, in 

 western Europe the maxima and minima of precipitation tend to be 

 progressively displaced in the sun spot cycle. 



The subdivision of the eleven-year period of rainfall Hellmann 

 explains by an assumed double influence of the variation in the 

 solar radiation during the sun spot period. First is a direct influence 

 arising from the equatorial region and acting indirectly as an in- 

 fluence upon the place itself. Hellman proceeds from the assump- 

 tion, now proved erroneous, that at the time of sun spot minimum 

 there is a greater radiation of the sun that at the time of sun spot 

 maximum. This increased radiation he thinks would act principally 

 in the equatorial regions of the earth to produce an increase of 

 temperature, evaporation and precipitation and thereby would in- 

 crease the energy of the total circulation of the atmosphere. This 

 equatorial influence would be delayed in reaching the higher lati- 

 tudes. But on the other hand the direct influence on the precipita- 

 tion in these latitudes themselves due to the sun spots would be 

 considerably weaker than in the equatorial regions. The impulses 

 derived respectively in the equatorial regions and in places of higher 

 latitude would exercise together either a cumulative or an interfering 

 action. It would be therefore conceivable, he thinks, that in one place 

 the minimum of rainfall would be associated with maximum of sun 

 spots, while in another place the opposite association would prevail. 



