308 



kept to the level of low-water. The low shingle bank at the south-east end of 

 the weir was crossed by a pile and brush dam, on the line shown on the plan, 

 carried up to the main bank of the river. 



This work was finished on March 25, 1867, and from that time, in floods, 

 about half of the river water passed across the shingle bank, scouring out first 

 a channel trending in towards the north bank, but eventually the large channel 

 shown on the latest plan, and this channel now took the whole of the river 

 water except in heavy floods, and the old channel tending towards the south 

 channel became smaller and smaller until it was nearly filled up. This would 

 have taken place earlier but unfortunately the work for some eighteen months 

 was neglected, and a gap of considerable width in the pile and brush part of 

 the weir, caused by the passage over it of an immense tree in a heavy flood, 

 was left open the whole time, thus considerably diminishing the scouring 

 action of the river on the shingle bank in floods. 



Art. LVL — On the Gyration of the Wind in New Zealand, with its 

 Characteristics in the Various Quarters. By W. S. Hamilton. 



(author's abstract.) 



[Read before the Wellington Philosophical Society, August 20, 1870.] 



The extreme changeableness of the weather in the Southern Hemisphere is a 

 well known characteristic of its climate. In this respect New Zealand is no 

 exception from other southern lands. This is caused, in these regions, 

 by the very regular rotation of the wind through the different quarters, 

 together with its strongly marked characteristics while in these quarters. The 

 striking regularity of these gyrations of the wind is one of the first indications 

 of a change of hemisphere which is encountered by the voyager from Europe, 

 where they are less regular from the greater mass of land producing local 

 winds and disturbing the general atmospheric currents of the world. The 

 moment the Cape is passed, these gyrations of the wind through N. to W., S., 

 and E., with their strongly marked characteristics of warm and dry for the 

 N., stormy and wet for the W., cold and damp for the S., and calm for the E. 

 winds are experienced, up to at least the 50th degree of latitude. 



Although the primary cause of these gyrations is now understood to be diie 

 to the earth's axial motion, modifying the direction of the great polar and 

 equatorial currents of the atmosphere, still there are many points not yet 

 positively settled in the theory of these winds. Some of these are the period 

 of rotation, whether constant for different latitudes, different seasons of the 

 year, and for different hemispheres, — whether it coincides in any way with the 

 ephemeris of the moon, — at what latitude the cycle is equal sided, that is when 

 the winds pass through the various quarters in about equal times, — at what 



