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Pressure of Air.
The mean atmospheric pressure in New Zealand between lat. 37° and 46° S. decreases from 29.981in. to 29′804in.; the average pres-
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sure being for all stations 29.919. For the corresponding north latitudes the average pressure is 30.005, but in the New Zealand area the fluctuations are much greater, and, though frequent, are tolerably regular in their periods. The maximum pressure occurs in April, and the minimum in November. The extreme range of the barometer is a little over 2in., and the average daily range from hourly observations is .043in.
The following are the observed averages of pressure for a few of the principal stations :—
I. Monthly Range of Air Pressure.
| Stations. |
Dec. |
Jan. |
Feb. |
Mar. |
April |
May |
June |
July |
Aug. |
Sept. |
Oct. |
Nov. |
Year. |
| Auckland |
0.657 |
0.681 |
0.728 |
0.756 |
0.909 |
0.961 |
1.043 |
1.051 |
0.965 |
0.886 |
0.827 |
0.835 |
1.417 |
| Taranaki |
0 740 |
0.883 |
0.886 |
0.981 |
1.028 |
0.917 |
1.094 |
1.138 |
1.024 |
1.051 |
0.929 |
0.752 |
1.594 |
| Southland |
1.193 |
1.122 |
0.854 |
1.039 |
1.079 |
1.240 |
1.250 |
1.248 |
1.197 |
1.094 |
1.240 |
1.169 |
1.732 |
II. Daily Amplitude.
| Dec. |
Jan. |
Feb. |
March |
April |
May |
June |
July |
August |
Sept. |
Oct. |
Nov. |
| 0.038 |
0.034 |
0.038 |
0.044 |
0.050 |
0.046 |
0.041 |
0.048 |
0.044 |
0.050 |
0.042 |
0.042 |
III. Hourly Fluctuation of Atmospheric Pressure and Elastic Force of Vapour.
A.M.
|
Mid-night. |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
| Bar |
+.013 |
−.001 |
−.003 |
−.012 |
−.010 |
+.004 |
−.006 |
−.006 |
−.005 |
−.003 |
−.001 |
−.011 |
| El. Force |
−.021 |
−.017 |
−.011 |
−.017 |
−.011 |
−.014 |
−.006 |
−.003 |
+.010 |
+.008 |
+.011 |
+.018 |
P.M.
|
Noon. |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
| Bar |
−.012 |
−.012 |
−.016 |
−.010 |
−.008 |
−.003 |
+.007 |
+.019 |
+.025 |
+.021 |
+.020 |
+.019 |
| El. Force |
+.020 |
+.025 |
+.021 |
+.013 |
+.008 |
+.009 |
+.003 |
−.002 |
−.006 |
−.006 |
3 1 |
−.011 |
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sure being for all stations 29.919. For the corresponding north latitudes the average pressure is 30.005, but in the New Zealand area the fluctuations are much greater, and, though frequent, are tolerably regular in their periods. The maximum pressure occurs in April, and the minimum in November. The extreme range of the barometer is a little over 2in., and the average daily range from hourly observations is .043in.