20 Dr. W. N. Shaw. On the General [May 16, 



" On the General Circulation of the Atmosphere in Middle and 

 Higher Latitudes." By W. N. SHAW, F.R.S., Secretary of the 

 Meteorological Council. Received May 16, Read June 2, 

 1904. 



In the course of an investigation into the trajectories, or actual 

 paths of air, by means of synoptic charts, which is still in progress,* it 

 became apparent that the paths of air taking part in cyclonic dis- 

 turbances near the British Isles when traced backward did not always 

 originate in anti-cylonic areas, but followed a track skirting the 

 neighbouring high-pressure areas and traversing sometimes a very 

 large part of a belt of the earth in a direction more or less parallel to 

 a line of latitude, and, on the other hand, air moving in the neighbour- 

 hood of a cyclonic depression did not invariably seek the nearest baro- 

 metric minimum, but sometimes passed on, leaving the circulation of 

 the depression on the left hand. 



Two suggestions at once arise from these results : First, that the 

 anti-cyclonic areas of the Atlantic take far less part, as sources of air 

 supply for travelling storms, than is usually attributed to them, and 

 secondly, that the motion of air in middle latitudes is more of the 

 nature of a passage round the pole in a general easterly direction, some- 

 times from north-west, sometimes from south-west, than is generally 

 supposed. 



The evidence in support of these suggestions will be considered 

 when the results of the investigation referred to are presented, but it 

 may be remarked here that the first suggestion, which would indicate 

 that the anti-cyclonic areas are of the nature of stable inert masses of 

 air round which the winds circulate rather than regions out of which 

 winds blow, is not inconsistent with the phenomena of anti-cyclonic 

 weather, and is borne out by the monthly wind charts of the South 

 Atlantic recently prepared by the Meteorological Council, and now in 

 course of publication by the Hydrographic Office of the Admiralty ; 

 and further that the existence of a general circulation of the atmos- 

 phere from west to east along middle latitudes right round the earth, 

 diverted to the northward along the eastern sides of the oceans and 

 back again to the southward across the land areas, is supported by the 

 recent summary of cloud observations by Hildebrandsson. f It is also 

 supported by the isobaric distribution for the 4000 metre level com- 



* Some of the results of this investigation have been already published, 

 ' Quarterly Journal Roy. Met Soc.,' vol. 29, p. 233, and vol. 30, p. 57 ; Monthly 

 Pilot Chart of the North Atlantic and Mediterranean,' February, 1904. 



t 'Rapport sur les Observations Internationales des Nuages'au Com ite Inter- 

 national Meteorologique,' aho ' Brit. Assoc. Report,' Southport meeting, 1903. 



