THE SUN-SPOT PERIOD AND THE VARIATIONS OF THE 

 MEAN ANNUAL TEMPERATURE OF THE EARTH/' 



By Cn. NoRDMANN, Docteur us sciences, 

 Astronome a V Ohservatoire de Nice. 



It has lono- been sought to discover if the various meteorolog-ical 

 phenomena of the earth, and particularly the temperature, are subject 

 to periodic variations other than the diurnal and annual periods depend- 

 ing on the rotation of the earth and its motion in the ecliptic. The 

 astrologers of the middle ages, who ali'ected to discern a relationship 

 between the great climatological changes of the globe and the con- 

 figuration of the sun and planets, and who based predictions upon such 

 phenomena, ma}' be considered perhaps as the pioneers in this line 

 of stud3\ 



During the eighteenth and the lirst half of the nineteenth centuries 

 men of science made numerous attempts to determine if meteorological 

 phenomena were dependent on the relative positions of the sun and 

 moon, and if consequently they could ])e associated with the various 

 periods common between these heavenly bodies, such as the Draconic 

 period, the Saros, and the period of nodes. These studies were influ- 

 enced by a long-standing and still prevalent belief, profoundly fixed 

 in the popular mind, that the moon exercises a preponderating 

 influence upon terrestrial climates. 



More modern and exact investigations have thoroughly tested this 

 traditional belief, and while it is shown that the moon actually appears 

 to produce tides in the higher regions of our atmosphere analogous to 

 those of the ocean, it is on the other hand established that our satellite 

 exercises no appreciable influence upon the temperature or climate of 

 the earth, and investigations along these lines have been at length 

 abandoned. 



I. 



The inquir}' was brought upon a new field when, in 1852, Sabine, 

 Wolf, and Gautier discovered that the phenomena of terrestrial mag- 

 netism were subject to variations of a period equal to that of the 

 sun spots. A little later Fritz discovered the same period in the 

 manifestations of the aurora borealis. Thenceforth it was natural to 

 inquire if all the other meteorological phenomena were not.equall}^ 

 subjected to the influences of sun spots. (We do not speak here of 

 more or less serious attempts which have been made from time to time 



"Translated from Revue Generate des Sciences, August, 1908, pp. 803-808. 



139 



