44 Transactions. — Miscellaneous. 



fall agaiu withiu a limited area, but continues to vise slowly at places beyond 

 those limits, while mthin them the wind suddenly " backs " to the north- 

 east, and a second hard northerly gale becomes rapidly developed within 

 this area; this second faU. usually reaches the same point as its predecessor, 

 the barometer then makes a second rapid increase which extends to the 

 whole colony, and a heavy gale from the southward is generally experienced, 

 this being the second southerly gale within the limited area already men- 

 tioned ; the lowest pressure in these gales generally ranges between 28-90 

 and 28-50, and the total fall at the southern extreme of the colony amounts 

 to about 1-25 inches. 



These areas usually travel about east by north, and the general, or I 

 beUeve it may be termed the normal routes of the gales which approach 

 New Zealand, are between W.S.W. and S.S.W., moving to the opposite 

 quarter ; but after a considerable period, generally not less than six months, 

 a depression comes in from the north-west, after whose passage the normal 

 route is resumed, and this change takes place, on some occasions, with such 

 promptitude that it is difficult to issue warnings in advance of it. Compar- 

 atively few of these north-west areas have come under investigation since 

 the principles of Forecast now in use have been fully in operation, but 

 there have been several of them, and there is no doubt that they, at times, 

 are of the class here described as double-centred. The depressions which 

 approach from the west of south are systems of multiple areas, some of 

 which are of intricate construction, and dm'ing their passage the wind 

 changes from north-east to north and west, veering as we term it m New 

 Zealand, but backing according to meteorological law ; and, as each suc- 

 cessive area approaches us, the wind moves from west of south to north of 

 west, which we term backing, but which is a veering movement according 

 to meteorological law. From these remarks it will be seen that the wind- 

 change in this colony is the same as in Great Britain, but during the 

 passage of areas from north-west the wind obeys the laws for the Southern 

 Hemisphere. 



An interesting subject for investigation is offered by the atmospheric 

 circulation of the temperate zones ; for in England and America the same 

 routes seem to hold good as in New Zealand, the depressions travelling 

 from south of west to the north of east, and being at times interrupted by 

 the passage of an area from north-west, and it thus appears that northern 

 countries are mainly supplied from a tropical dh-ection, the balance being 

 restored from a polar quarter, whereas our supply is generally derived from 

 the polar side, and recouped, as it were, from the tropic. 



A marked feature of this Forecast are binding isobaric contours, or 

 binding-hnes, which enclose the secondary and minor areas, and which are 



