NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC 243 



the earth's surface are the primary cause of changes of precipitation, 

 rainfall, or great movements of the air and fluctuations of the 

 barometer. He comes to the final conclusion of his investigation 

 "that all the ordinary phenomena of temperature, rainfall, and 

 winds are due to purely terrestrial causes and that no changes occur 

 in the sun's radiation which have any influence upon them." We on 

 the contrary have found that the variations in the solar activity play 

 a very great part in variations in air pressure, temperature, and 

 precipitation, and have come to the conclusion that it is the air pres- 

 sure distribution which in the first place is influenced and produces its 

 secondary actions o'n all the other meteorological elements. 



AIR PRESSURE DISTRIBUTION AND SOLAR ACTIVITY 



In the investigations which we have described of the variations of 

 the surface temperature of the ocean we found that these were 

 prinicipally determined by the air pressure distribution, that is to say, 

 by the winds of the individual months. This circumstance may 

 give a hint where to find the cause which we are seeking. 



Our investigations of the air pressure variations at the different 

 meteorological stations on the land give, to be sure, no positive re- 

 sult indicating an explanation of the dependence between the atmos- 

 pheric variations and the solar activity. On the other hand, it is not 

 excluded that the explanation may be sought in the differences of 

 atmospheric circulation ; for the variations in the air pressure at 

 individual stations as a rule give no real expression of the disturb- 

 ances of the atmosphere, or the variations in atmospheric circulation 

 over great regions. Such an indication must be found in the varia- 

 tions of the air pressure gradients. It would be easy to trace the 

 variations in these gradients if one could only be sure of the dif- 

 ference in air pressure at two different stations, but we have already 

 in another connection remarked upon the difficulties involved. 



AIR PRESSURE DIFFERENCE COLOMBO-HYDERABAD 



Nevertheless we have made such an investigation for a region 

 which we have already treated extensively, determining for this pur- 

 pose the air pressure difference for each month for Colombo, in 

 Ceylon, and Hyderabad, in north India. It is to be remarked that 

 the air pressure difference at these stations is inverted during the 

 year since the air pressure maximum in winter lies north of India 

 in interior Asia and in summer south of it, at which time interior 

 Asia has an air pressure minimum. These conditions control the 

 variations of the monsoon winds. 



