CORRELATION. 205 



extreme north the positive correlation was very great, being -|-45 with a probable error of 

 10 at Tounsville. 



It appears as though to the north of Australia there is a large region in which the 

 pressure changes take place in the same sense as the changes over the Antarctic and between 

 the two a region in which the changes are reversed. The boundary of the two regio-ns 

 appears to vary and to swing backwards and forwards. In 1902-03 the northern area of 

 positive correlation was highly developed, and it encroached on the area of negative correla- 

 tion, the boundary between the two areas being near Sydney. In 1911-12 the area of negative 

 correlation was more strongly developed, and the boundary of negative correlation was pushed 

 north to near the northern coast of Australia ; Thursday Island, Daly Waters and Tomisville, 

 being the only Australian stations then having positive correlation coefficients. 



This connexion between the pressure departures over the Antarctic and surrounding regions 

 is most interesting and still more important. It appears that the Antarctic is one of the 

 great ' centres of action ' of the world and further investigation is imperatively demanded. 

 A great deal more work has been done than is given in the above summary, amongst other 

 results it has been fomid that all the correlations are more pronounced when the means of 

 three months' pressure are compared instead of the means of single months. The investiga- 

 tion is not yet finished, and as its value will be greatly increased if it is founded on more 

 observations than those at present available, it has been decided to await the publication 

 of the pressure data obtained on Shackleton's two expeditions to McMurdo Sound, which will 

 increase the data available from four years to seven, before closing the investigation. 



