
DIURNAL OSCILLATIONS OF THE BAROMETER. 405 
Inch. Inch. Inch. 
Valentia, : : 0:010 | Dublin, . : ; 0°012 | Edinburgh, . : 0-011 
Helston, é r 0:007 | Oxford, . , . 0:023 | Christiansand, F 0016 
Parjs, '. : : 0:020 | Ostend . . : 0004 | Christiania, . : 0032 
Geneva, : : 0-048 | Brussels, - : 0°021 | Upsal, . : 5 0:024 
Turin, . : J 0:051 | Vienna, . 3 A 0°050 | St Petersburg, ; 0:002 
Rome, . : fe 0°035 | Odessa, ‘ 4 0:024 
Reggio, . : : 0:008 | Tiflis, . : - 0°084 
No such enormous differences, or anything that could be regarded as an 
approach to them, occur during the summer of the southern hemisphere, 
between the oscillations at places in or near the same latitudes. The following 
illustrations for January will show this :— 
Lat. E. Long. W. eaien. 
a i a 1 nen. 
Santiago de Chili, : 5 : ; 33 26 70 37 0:040 
Long. E. 
Capetown, : : i 3 . 33 56 18 27 0°035 
Graham’s Town, . i . i . 33 18 26 29 0:045 
Petermaritzburg, . ‘ é : ‘ 29 30 30 2 0:056 
Freemantle, : : i 5 ; 33 2 115 45 0:048 
Deniliquin, : : : : : 85 32 145 2 0-087 
Sydney, ~- ‘ 5 : ‘ ; 33 52 151 11 0:065 
Auckland, . : 5 : ; 3 36 50 174 50 0:035 
In this case the extremes are 0°087 inch at Deniliquin, on the Murray River, 
Australia, and 0:035 inch at Auckland, in the north of New Zealand, these 
being respectively the most inland and most insular stations of the group. 
Whatever be the cause or causes on which the diurnal oscillations of the 
barometer depend, the influence of the relative distribution of land and water 
in determining the absolute amount of the oscillation in particular localities, as 
well as over extended regions, is very great. From the facts detailed above, it 
will be seen that this influence gives a strong local colouring to the results, 
particularly along the coasts, and that the same influence is extensively felt 
over the Channel, the Mediterranean, the Atlantic, and other sheets of water 
on the one hand, and on the other, over the inland portions of Great Britain, 
Europe, and the other continents. It will also be observed from the charts, 
that the lines are as strongly marked as are the lines which show the distri- 
bution of the temperature, pressure, &c., of the atmosphere, and that they show 
equally as great abnormal deflections in particular seasons over particular regions. 
The regions more or less extended, to which more special attention has 
been drawn, have annual maximum and minimum periods, depending very 
largely, though not nearly altogether, on the position of the sun, the humidity of 
the air, and the direction of the wind, particularly considered as a sea or a land 
wind. The general course of the lines over the globe has also a well-marked 
annual period—the minimum of deflection from the course of the parallels of 
latitude occurring in January, the amount of the deflection being then small, 
and the maximum deflection in July. . 
VOL. XXVII. PART III, 5 0 
