ScHAW. — Interaction of Cyclones. 569 



highest pressure recorded being at Eotorua, 30-5 ; a divide 

 with opposite circulations running round the west, north, and 

 east of the northern part of the North Island. 



This small anticyclonic "high" seems to have been 

 formed during the blending of the outer parts of the two 

 storms by the rapid onward movement of the antarctic storm, 

 and probably the peculiar bend in the circulation of the 

 antarctic isobar 29*6 at New Plymouth gives an illustration of 

 the way in which the more rapidly progressing storm blends 

 with the other which is moving more slowly. (See Plate LIV., 



fig- 1-) 



On the 27th June the tropical storm has disappeared 



entirely; so also has the small anticyclonic "high" which 

 was formed over the North Island. Thev seem to have 

 neutralised one another, while the antarctic cyclonic circula- 

 tion has closed in on both sides, and the eastern edge of its 

 valley has advanced eastwards about half - way between 

 Christchurch and Chatham Island, stretching north also into 

 the open sea to the east of Napier. (See Plate LIV., fig. 2.) 



The onward rate of progress of the tropical storm moving 

 from north-west to south-east was about two hundred and 

 fifty miles in twenty-four hours, while that of the antarctic 

 storm moving eastward was about five hundred miles in 

 twenty-four hours, both being retarded by the land which 

 their tracks crossed. These tracks crossed each other at an 

 angle of about 45° ; both were moving eastwards, but as the 

 tropical storm moved also to the south its eastvi'ard velocity 

 was not more than one-fourth of that of the antarctic storm, 

 which therefore overtook it, and blended with it. 



In the case last year, when two such storms repelled one 

 another, they were moving, one from the north and the other 

 from the south, without much easterly tendency in either 

 case. 



It is abundantly evident from my observations of a 

 balanced wind-vane during the last year that the circulation 

 in cyclones is chiefly upwards in combination with the hori- 

 zontal circulation, and in anticyclones it is downwards ; and 

 the upward motion in the former is more apparent near the 

 earth's surface than the downward motion in anticyclones, 

 which is quite what might be expected. As yet I have been 

 unable to detect any distinct indication of the upward motion 

 being greater or less in the front part or rear part or on either 

 side of a moving cyclonic circulation, and the motion is so 

 complicated that no one has yet been able to follow it accu- 

 rately. The numerous observations that are now being made 

 in Europe and America with kites and balloons will, I hope, 

 soon throw light on the subject, and may enable us to under- 

 stand the interaction of cyclones upon one another. 



