40 Transactions.— Miscellaneous. 
Art. IV.—On the Principle of New Zealand Weather Forecast. 
By Commander R. A. Epwis, R.N. 
Plates I-III. 
[Read before the Wellington Philosophical Society, 11th October, 1879.] 
Tue subject treated of in this paper is one which has for some years past 
received great attention in other countries, and their publications upon 
Weather Forecast give us ample information as to the method by which 
their predietions are arrived at, and the measure of success which has 
attended their efforts. It is now proposed to give some description of the 
manner in which the Weather Forecast of this colony is carried out. The 
subject is one which may be considered of general interest, and the method 
of procedure differs in some respects from that practised in other coun- 
tries ; but as it has already stood the test of some remarkably changeable 
seasons, with a large percentage of success, it seems now desirable to invite 
further investigation in the matter. * 
In the first efforts to arrive at some conclusions as to probable changes 
in the weather, the principal difficulty which eame under consideration was 
the deflections which the mountainous nature of the country seemed to have 
power to create, not only in the direction of the wind, but also in the dis- 
tribution of pressure. For instance, an isobar will generally run very fairly 
from Russell to Grahamstown, Tauranga, Gisborne, and Napier; but 
instead of continuing toward Castlepoint and Lyttelton, it will be found to 
curve inland and westward toward New Plymouth, then to turn southward 
between the latter place and Wanganui, and return eastwards towards Castle- 
point which it leaves on its right. Now, it will be found upon investiga- 
tion that pressure is nearly always higher at Westport and Hokitika than at 
Kaikoura, which itates this isobar bei g again drawn westward, i.e., back 
through Cook Strait, and passing Cape Farewell turn toward south to West- 
port and Hokitika, from which point it returns eastward, passing out be- 
tween Blenheim and Kaikoura. A second isobar should have commenced 
at Auckland and run toward Taupo, Wanganui and Blenheim; and a third 
might be reasonably expected to pass over Westport, Hokitika, Queenstown, 
and Balclutha ; but it is evident that, according to meteorological law, they 
must follow the first line of equal pressure upon that side which will show 
that they define the position of a lower pressure, and this necessitates their 
following it through all its sinuosities, but westward of it. 
Such distributions of pressure were found to be by far the most preva- 
lent state of affairs, and in many instances the curves were much more dis-* 
torted than shown on the diagram ( PI. IL., Jig. 1), but it seemed probable 
that other disturbing influences must also be in existence, and tending to 
