SMITHSOXIAN MISCELLANEOUS COLLECTIONS 



VOL. 89 



over, the general trend of the ]Dressure during the past 50 years has 

 been upward. This is true throughout the equatorial region from 

 northern Brazil to northern Australia. It w^ill be noted that there are 

 maxima every 2 to 4 years, which in the plot are marked a, b, c, d. 

 There are also longer oscillations, which may be brought out by 

 smoothing the curves. Consecutive or overlapping means of 3, 4, and 

 5 years were tried ; then a second smoothing of the means of 3 was 

 tried, so that the formula became ^2l''2l^ A second smoothing of 

 the means of 4 was also tried with the formula -gSi^Si^. The results 



Fig. 5. — Smoothed means of pressure at stations in high latitudes (continuous 

 lines) compared with smoothed means at a tropical station (dotted lines). 



of this last formula gave the smoothest curves ; but the second means 

 of 3 were more easily obtained, so that the first formula was adopted 

 for the smoothing, although in some cases the first means of 5 were 

 used instead. The dotted curves given in figure 4 are from the 

 second means of 3 (first formula). The data for these curves were 

 obtained from World Weather Records, Smithsonian Miscellaneous 

 Collections, vols. 79 and 90. 



In figure 5 the smoothed means for Colombo are compared with 

 similar smoothed annual means of pressure in high latitudes. The 

 pressure oscillations are larger in high latitudes than in the Tropics, 

 so that Colombo is plotted on a more open scale. It is seen that the 



