REPORT ON ATMOSPHERIC CIRCULATION. 67 



pressure in Australia the winds of the district where the temperature has risen to 

 95° blow from the interior of the arid portion of this continent. 



In this month pressure has continued to fall over the whole of the southern 

 hemisphere. The low pressure in the north of the Pacific remains much as it was in 

 October, except that it has extended over Behring Straits ; the low pressure in the 

 north of the Atlantic is nearly the same as in the previous month, except that it is 

 several degrees of latitude to southward, and a subsidiary satellite depression has 

 appeared to the north of Norway. Pressure has also fallen over the north-eastern half 

 of the Atlantic as far as lat. 60° N. ; but the most remarkable fall is that which occurs 

 over all Europe, except in Spain and Portugal and in the west and south of France. 

 This general fall of pressure over the north-eastern part of the Atlantic, and to the 

 eastward over Europe to long. 45° E., taken in connection with a simultaneous large 

 increase over Iceland and Greenland, gives the explanation of the secondary maximum 

 of easterly and northerly winds which prevails over a large portion of Europe in 

 November, with the reduced rainfall which accompanies them. 



There are other low-pressure centres in the Indian Ocean from Borneo to Ceylon, 

 in Africa, in the regions of the lower Amazons, and in the north-west of Australia. 

 The peculiarities of the distribution of the pressure over the seas of southern Europe 

 are even more pronounced than in October, showing that distribution is in the strongest 

 manner mainly influenced by the irregular distribution of land and water over the same 

 regions. 



Of the four anticyclones of the two great oceans, the most pronounced is that to 

 the westward of the heated plains of the Argentine Eepublic, and the least that in the 

 North Atlantic. 



The anticyclone of Asia indicates a pressure of 30 '40 inches, and its system of 

 isobars and outflowing winds on all sides shows that it has now acquired its strongly 

 marked winter characteristics. The other anticyclones are in the Indian Ocean to the 

 west of Australia, in the Pacific to the north-east of New Zealand, a subsidiary one 

 being also in Spain. The courses of the isobars of 29"95, 29 - 90, and 29'85 inches from 

 the north-east of Africa to Tonkin illustrate in a remarkable manner the influence of 

 the ocean in lowering, and of the land in augmenting, pressure at this time when 

 temperature is rapidly falling. Over all India the surface winds are northerly, but 

 the different directions in different districts possess great interest in their relations to 

 the undulating courses of the isobars. 



From the greater prevalence of northerly and easterly winds the maximum rainfall 



for the year occurs in November nowhere in Europe, except in the Mediterranean 



region marked out by the isobar of 30*00 inches, and eastward so as to include Greece. 



December. — The mean temperature of the whole of the earth's surface enclosed by 



the Arctic Circle is under 32°, and the isothermals of -25° embrace a large portion of this 



