560 Transactions. — Physics. 



With the departure of the second anticyclone follow changes 

 somewhat similar to those just described, but varying accord- 

 ing to the energies of the succeeding disturbances so long as 

 anticyclonic and wave-pressures follow each other. 



The lowest pressures of these waves always pass to the 

 southward of this country : they usually include within their 

 limits all parts of it lying to the southward of East Cape and 

 Raglan, but some are of much greater area, and extend north- 

 ward to the Three Kings Islands, and sometimes to Norfolk 

 Island. These low-pressure waves occupy on an average six 

 days from the date of their passing the meridian of Cape 

 Leeuwin to the meridian of the South Cape of New Zealand. 



The upper and intermediate clouds which precede and 

 accompany westerly wave-pressures are cirrus, cirro-stratus, 

 and cirro-cumulus. They are generally first seen in the west, 

 and travel towards east, changing from west towards north- 

 west — i.e., from left to right — as pressure decreases, and from 

 north-west to west, or from right to left, before it increases, 

 alternating in this manner with the passage of each westerly 

 wave, but finally continuing the right - to - left movement 

 towards south-west and south with ihe rising barometer as 

 anticyclonic pressure approaches. When cirrus clouds have 

 their tips curled back towards the direction they come from, 

 or increase quickly, and are moving fast, high winds generally 

 follow soon ; and when they are seen coming from between 

 north-west and north they usually indicate a wave-pressuie 

 of greater than ordinary extent. Alto-cumulus clouds come 

 from between west and south, and generally precede anti- 

 cyclonic pressure. Solar and lunar coronae. and also imper- 

 fect halos, are seen with these disturbances. With westerly 

 wave-pressures there is usually seen in the eastern sky at 

 sunset a well-defined pink or rose colour, whose upper edge 

 gradually pales into the blue above it, but very little and 

 sometimes none of the ordinary sunset tints are seen in the 

 west ; the rose colour sometimes deepens most distinctly for a 

 minute or two, then moving upward fades quickly and dis- 

 appears ; it is succeeded by a pale yellowish colour, above 

 which there is frequently a pale green, and patches of pale 

 orange are seen low down toward the south. 



Cyclones. 

 Cyclones are easiest described as being low pressures of a 

 bluntly oval shape much compressed on the line of advance, 

 and having their pressure always decreasing inward to a 

 central minimum of an almost circular shape. Their wind- 

 rotation in this hemisphere is from left to right, or in accord- 

 ance with the movements of the hands of a watch. Fig. 5 

 shows the wind and pressure changes caused by the eastward 



