Meeson. — The Bainfall of New Zealand. 561 



Moreover, general!}- the rain comes with a westerly wind 

 of some kind rather than with one from any other quarter. 

 Very little indeed comes from north or south upon the whole, 

 and not much from any quarter of east, although occasional 

 heavy storms from north-east or south-east make one or the 

 other of those points of the compass take the second place 

 here and there in the tables. 



The prevalence of westerly weather in New Zealand is not 

 at all exceptional, but just what our latitude would lead us to 

 expect. In the Temperate Zone twenty-miles-an-hour west- 

 erly winds usually predominate, as in the Torrid Zone easterly 

 winds blow almost continuously. The latter are nothing but 

 the Trades, as the former are the Eetm'n Trades, which, over- 

 flowing in tlie first place fi'om the equatorial regions, set off as 

 upper currents towards the lower pressures of liigh latitudes — 

 i.e., in our Southern Hemisphere, in a southerly direction ; but 

 on account of their coming from a portion of the earth where 

 the rotatory motion is greatest to a part where it is less, we 

 see, by adapting Hadley's law, that they get an easterly ten- 

 dency — i.e., come to us in the first place as north-west and 

 then as west or south-west winds. Up to lat. 23^-° they 

 are upper winds, the currents of air below them being, of 

 course, the south-east trades. But at the Tropic of Capri- 

 corn these upper winds cross the lower ones, and sweep the 

 surface of the earth. At some seasons the point of crossing 

 is nearer the equator than at other seasons, but wherever it 

 may be it produces a belt of calms and variable winds or 

 cyclones rotating and succeeding one another in the opposite 

 direction to the hands of a watch. But the north-west or 

 anti-trade winds move on polewards. Being equatorial in 

 origiu, ihey are warm and moist. They lose and gain heat iu 

 their travels by ascending and descending intervening mountain- 

 chains ; also by licking up moisture as they pass over the 

 ocean, and discharging it again when by any means whatever 

 their temperature is lowered. Althougli they are interfered 

 with by the irregularities of pressure consequent on the varia- 

 tion of temperature which arises from difference of latitude 

 and the unequal distribution of land and water, they are won- 

 derfully persistent even so far as 50" S. lat. ; and for some 

 degrees before they reach that latitude, following the general 

 law which expresses the regular succession of the winds to one 

 another, they haul or veer to the right hand — i.e., to the place 

 where prevails the lowest pressure — and become the well- 

 marked and widely-extended westerly winds of the " roaring; 

 forties." These, iu then- various forms of cyclones, y-depres- 

 sions, wedges, and secondaries, dash up against our western 

 mountains, which he riglit athwart their course, and there 

 quickly lose their moistm-e, and are largely deflected to the 

 36 



