180 
JOURNAL OF THE TLYMOUXn INSTITUTION. 
equator to the pole. These currents result from the unequal tem- 
perature of the earth's surface, and nearly all that remains of the 
general history of the atmosphere is included in the account of the 
causes which disturb the uniformity of their course. Westerly 
gales are far more destructive to shipping on and near our coasts 
than easterly gales, the most destructive being from south-west ; 
but there seems less occasion to give warning of southerly storms 
by signals than of northerly, because the former are preceded by a 
falling barometer, and by a higher temperature than usual; whereas, 
on the contrary, storms from a polar quarter are sometimes sudden, 
and are usually preceded by a rising barometer, which often mis- 
leads, especially if accompanied with an appearance of fine weather. 
The storms which pass over the British Isles are found to act in 
strict accordance with the ''cyclonic" theory. In many cases, 
however, the phenomena become highly complicated, owing to the 
interference of two or more cyclones. The heaviest storms which 
pass over Great Britain generally have a progressive motion from 
south-west to north-east, and the most frequent track of their 
centres is a line passing in that direction across the JN'orth of Ireland 
and the South of Scotland. The numerous balloon ascents have 
not only yielded abundant proof of the pressure of air currents at 
various elevations, quite independent of each other, having very 
different temperature, and moving with apparent steadiness in some 
fixed direction ; but a contrast or diversity in force between the 
currents prevailing at different elevations is invariably observed. 
The lecturer could scarcely feel confident that the electrical phe- 
nomena exhibited during heavy gales were not effects rather than 
causes. Much now was said on the subject, and the question was 
asked in passing, "Are we in a position to say that actinism does 
not assist in creating some of the atmospheric disturbances now 
wholly unaccounted for?" If electric states of atmosphere can 
convert oxygen into ozone, light in its diflPerent degrees of intensity 
cannot well be supposed without influence on the inorganic parts 
of the aerial medium through which its passage lies. In conclusion, 
the system of storm signals and warnings now in use was noticed, 
and a hope expressed that before long some such a system as that 
which has for years been in use both in Paris and St. Petersburg, 
viz., the publication every morning of a sheet containing the 
mapped climate of all Europe of the day but one before, may be 
adopted in England. 
