NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC 167 



at minimum, but the period of air pressure variation lags behind the 

 sun spot period. 



Blanford (1879, 1880) extended his investigations over a larger 

 region including observations at Batavia, Singapore, Colombo and 

 several Indian stations and also Mauritius. He showed that in the 

 whole Indo-Malayan region the air pressure varies oppositely with 

 the sun spots. These variations were most clearly and regularly 

 developed at island stations near the equator. But at the same time 

 he obtained the highly interesting relation that as Hill and Archi- 

 bald had found fo'r St. Petersburg, namely, the air pressure there 

 varied directly with the sun spots, also that for stations further east 

 in Russia and Siberia as Ekaterinburg and Barnaul the same condi- 

 tion prevailed. This was also found less marked for the stations 

 Bogoloves and Slatoust in the Urals. Furthermore he showed that 

 these variations going directly with the sun spots prevailed only for 

 the air pressure in winter in St. Petersburg, Ekaterinburg, and 

 Barnaul, while his curves for the summer had a tendency to go in 

 the opposite direction to the winter curves. He did not notice that 

 the amplitude of his winter curves decreased in magnitude from St. 

 Petersburg eastwards, nor did he note the extremely interesting 

 thing that his summer curves for Ekaterinburg and Barnaul in 

 general have the same character as both the summer curves and the 

 yearly curves of the air pressure at the Indian stations. The air pres- 

 sure in summer in the Siberian stations varies almost oppositely 

 with the sun spots. 



From this we see that between Russia and Siberia on the one hand 

 and the Indo-Malayan region, perhaps also including the Chinese 

 region, on the other hand, there is in winter an opposite and periodic 

 oscillation of the air pressure in such a manner that while in winter 

 in west Siberia and Russia maximum pressures prevail at sun spot 

 maximum, minimum prevails in the Indo-Malayan region and vice 

 versa at sun spot minimum. As he expresses it in a later publica- 

 tion (1891, p. 586) " in years of maximum sun spots a larger portion 

 of the tropical atmosphere is transferred to high latitudes in the 

 winter hemisphere, which again implies a disturbance of atmos- 

 pheric equilibrium in that epoch between the tropics and the circum- 

 polar zone and therefore an increased intensity of the disturbing 

 agent." In the tropical stations he found a slight difference between 

 the variations in air pressure in summer and winter. It behaved in 

 both seasons of the year oppositely to the sun spots. 



Blanford was of the opinion that the observed variations in air 

 pressure must have their seat in the higher regions of the atmos- 



