Schaw. — AtmospJieric Motion. 379 



and that south of 50° or 55° S. latitude in the southern half 

 of their circuits easterly winds are encountered. 



(3.) That further south still anticyclones usually exist, 

 and beyond them, in about latiude 75° S., a belt of cyclones 

 cause the very low barometer usually observed there in the 

 summer months. 



(4.) That the occasional displacements of the belts of anti- 

 cyclones and cyclones farther north or south than their 

 normal position which we observe here appears to be also 

 the case with the alternate belts of cyclones and anti- 

 cyclones which exist between us and the pole. 



(5.) That in cyclones there is an upward movement of the 

 air, and in anticyclones there is a downward movement, each 

 being accomplished in many complicated swirls, so that some- 

 times the inclination of the motion is, in gusts, as much as 

 40° from the horizontal, although the general upwards or 

 downwards motion is very much less. 



(6.) That it is the total effect of the upward or downward 

 motions in the strata of the atmosphere above any place, at 

 any time, which varies the atmospheric pressure shown by 

 the barometer at that place. 



(7.) That, while the barometer shows accurately the de- 

 crease of atmospheric pressure caused by the ascent of a 

 mountain in calm weather, this mode of ascertaining heights 

 is much interfered with in high winds owing to their deflection 

 upwards by the slopes of the mountain. 



(8.) That cyclones and anticyclones are complementary 

 one to the other, and that apparently the rising air in the 

 cyclone is replaced chiefly from the falling air in the following 

 anticyclone. 



(9.) That when cyclones collide, if moving in nearly the 

 same direction they coalesce, if moving in nearly opposite 

 directions they repel one another. 



(10.) That occasionally small cyclonic circulations are 

 originated in the neutral zones between two anticyclones ; 

 these move eastward round the more eastward of the two 

 anticyclones. 



(11.) That the cyclones which sometimes reach New Zea- 

 land from the north, with easterly winds at first, are tropical 

 cyclones, originating in tropical regions northward of the belt 

 of anticyclones, apparently caused by a concentration of heat 

 in some place. Their forward motion is irregular, but it 

 generally is in a southerly direction, and inclining to the east 

 as they pass between two anticyclones. It is these tropical 

 cyclones which sometimes meet one of the regular antarctic 

 cyclones, and either blend with it or they repel one another, 

 according to the direction in which the tropical cyclone is 

 progressing at the time of meeting. 



