244 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 'JO 



In figure 91, curve II gives the consecutive twelve-monthly means 

 of air pressure difference between Colombo and Hyderabad. Curve 

 III gives the consecutive twelve-monthly means of air temperature 

 at Batavia. As the reader may see, the principal variations in these 

 two curves go approximately in opposition. An increasing air pres- 

 sure difference between Colombo and Hyderabad corresponds to a 

 lower temperature at Batavia and vice versa. This was indeed to be 

 expected ; for if the yearly air temperature difference is small there 

 would be in the course of such years a relatively small mean motion 

 of the air, and so the temperature in Batavia would tend to rise and 

 vice versa. 



Curve I-b shows the air pressure variations in Bombay after 1900 

 according to Arctowski's publication of 1912, given in twelve- 

 monthly consecutive smoothed values. As already stated this curve 

 runs within this time interval oppositely to the temperature of 

 Batavia, and follows the curve for the air pressure difference between 

 Colombo and Hyderabad. If, however, we follow the temperature 

 variations of Bombay further back in time we see, as already stated, 

 that they go in the same direction as in Batavia, and therefore 

 oppositely to the variations of the air pressure difference. This is 

 shown by curve I-a for the years 1880-89 (after Arctowski, 1915) 

 and also by curve IV. In the absence of twelve-monthly consecu- 

 tive smoothed temperature values for the whole time interval men- 

 tioned, we give the curve by aid of the mean temperature values for 

 the whole year. It is obviously not so accurate as those which depend 

 upon twelve-monthly consecutive smoothed values, but neverthe- 

 less it gives the character of the variations. While the variations 

 of this curve up to about 1896 go oppositely to the variations in 

 the temperature curve of Batavia, before 1896, they are very simi- 

 lar to the variations of the Batavia curve, and so go oppositely to 

 the variations in the air pressure difference between Colombo and 

 Hyderabad. 



Thus we find again the often appearing sudden reversal of the 

 agreement between two curves of which one originally agrees with 

 the other and then suddenly begins to march in the opposite direction. 

 This often occurs in the comparison of two temperature curves at 

 very different regions of the earth and also in the comparison be- 

 tween a temperature curve and an air pressure curve. We note 

 in regard to it that the year 1896 in which the two curves we are 

 discussing suddenly entered upon opposite courses corresponds with 

 the time between 1894 and 1897, when the solar activity showed 



