A.—MATHEMATICAL AND PHYSICAL SCIENCES 43 
monthly seasons of June to August it was —0-46. Between Samoa and 
Batavia December pressures the coefficient was —o0-38, and for the 
season December to February it was —o-60. ‘Thus it is between the 
characteristics that persist over months, not over days or weeks, that 
relationships exist. 
Being forced off short-lived phenomena we search for an explanation 
in terms of slowly changing features, such as ocean temperatures ; and 
the big variations from year to year in the amount of pack ice in the 
antarctic seas forces itself on our attention. But here the reports of 
twelve years from the South Orkneys yield a relationship of only 0-32 
with the southern fluctuation, instead of about 0-9, as we should want in 
a prime cause ; and the variations at the South Orkneys come after rather 
than before those of the southern oscillation. The biggest ocean region 
is the Pacific, and as an index of its seasonal water temperature we 
may use the corresponding air temperature of Samoa, which shows a 
greater persistence than any factor in the world as yet examined ; the 
relationship between its summer and autumn values is as large as 0-94. 
But unluckily the correlation coefficients show clearly that it is mainly 
the southern fluctuation in winter that controls the Samoa temperature. 
Thus a short-cut to the explanation of our fundamental problems seems 
as far away as ever. Our three big fluctuations each form a system of 
_ changes which are apparently held together by meteorological links : 
and there is, in my opinion, as yet no satisfactory proof of any free periods 
associated with them. 
Let us now consider in what direction new developments seem likely. 
A moment’s reflection will convince us that in view of the variations of 
rainfall over large areas, such as Brazil and Central Africa, which are 
scarcely affected by the three big fluctuations, there must be others, 
some of which are probably on a big scale. For example we should, on 
the analogy of the northern oceans, expect a fluctuation of pressure 
_ between the antarctic low pressure belt and the high pressure belt of 
—30°S. Weare at once reminded of the marked opposition which Simpson 
_ found during the short period of four years for which data were available 
_ between pressure at McMurdo Sound and that in a belt round the earth 
_ extending from about 25° S. to about 50°S. All students of this subject 
have found it natural to regard the fluctuations in the amount of pack 
_ ice in the antarctic seas as likely to control sea and therefore air tempera- 
tures over large regions, and the most southern station from which as 
_ Many as twenty-five years of data are forthcoming is the South Orkneys. 
_ Its winter pressure does show the opposition that we should expect with 
that of Australia, but not with the high-pressure region of South America 
, gh-p § 
or Mauritius ; so that it gives little support to the view that there is a 
general pressure oscillation between the low and the high pressure belts 
of the southern hemisphere. On the other hand, the air temperature at 
the South Orkneys may be regarded as an index of the sea temperature : 
and as the ocean current through the Drake Passage would take about a 
year to reach South Africa, we are not astonished at the relationship of 
0°56 between the South Orkneys air temperature in winter and that of the 
next winter at Cape Town. ‘This is not, however, as close as the corre- 
