
DIURNAL OSCILLATIONS OF THE BAROMETER. 403 
by noting the course of the line of oscillation of 0:040 inch, which in March 
begins to overspread a larger portion of the region indicated. It continues to 
increase and extend steadily from month to month to the annual maximum in 
August, after which it diminishes in extent from month to month till in De- 
cember it appears only in the Spanish Peninsula. — 
Quite analogous to the above are the facts of the oscillation as they are 
presented by the inland districts of the Italian Peninsula, where, as in Spain and 
Portugal, numerous observations are available for a closely approximate defini- 
tion of the geographical distribution of this oscillation. Indeed, the copious 
data obtained from these countries with respect to this oscillation are of the 
highest meteorological value. 
At Bilbao, Oviedo, Coruiia, Oporto, Lisbon, Gibraltar, Barcelona, Marseilles, 
Genoa, Leghorn, Naples, Reggio, and all places on and near the sea, the winter 
greatly exceeds the summer oscillation, and the more strictly insular the situa- 
tion, the greater is the difference. This peculiarity would appear to extend 
farther inland over the comparatively broad peninsula of Spain than over the 
narrower peninsula of Italy ; and these two countries may be pointed to as 
likely yet to furnish the key to the explanation of this marked feature of the 
oscillation under discussion, which doubtless plays an important part in 
determining the diurnal changes peculiar to sea-side climates as regards wind, 
temperature, and humidity. 
On the contrary at Madrid, Zaragoza, Huesca, Jaen, Campo Maior, Mont- 
pellier, Dijon, Metz, Geneva, Milan, Vienna, Prague, Leipsig, Halle, Upsal, and 
other continental situations, the spring or summer exceeds the winter oscillation. 
The influence of the Channel, the North Sea, and the Baltic on the regions 
adjoining is similar to that of the Mediterranean. A comparison of the coast 
stations of Holland, Belgium, and North of France with neighbouring inland 
stations will at once show this; whilst the influence of Great Britain on the 
other hand resembles that of the Spanish and Italian peninsulas ; but in both 
cases the amount of the disturbance is much less. ‘The few observations we 
have from the Black and Caspian Seas point in the same direction. 
But it is over the Atlantic and regions bordering it, where in certain seasons 
the greatest amount of disturbance occurs in the deflection of the lines, par- 
ticularly those representing 0°040, 0-020, and 0:010 inch of oscillation, from 
what may be regarded as their normal course. In January these lines run 
tolerably parallel with the latitude, but in March they begin decidedly to curve 
southwards over this ocean, thus indicating a diminution in the amount of the 
oscillation as compared with the land adjoining, just as has been seen in the 
case of the Mediterranean and other sheets of water. The disturbance goes on 
augmenting till it reaches the maximum in July, after which it begins to diminish 
month by month, till in the end of October it has all but disappeared. 
