SCIENTIFIC SUMMARY. 
407 
centre of the storm should have passed near Ballinasloe, when the wind 
should have changed through 180 degrees. But as this occurrence did not 
take place, this storm could not have been a cyclone. — Vide Dublin Quar- 
terly Journal of Science, January, 18G4. 
How the Storm of the 2nd and 3rd of December originated . — M. Vaillant 
has presented a memoir to the French Academy on this subject. He con- 
ceives that storms such as the above are produced by the collision which 
takes place between two currents of air, one of which is warm, the other 
cold, the latter being produced by heavy falls of snow in certain localities. 
He ascribes the storm of the 2nd of December to the meeting of the moist 
and warm wind, which at that time overspread Europe, with the cold wind 
which blew in every direction ; but in France from the north-west, and 
which was produced by the cold effected by a heavy fall of snow in Scot- 
land. What supports this view is the fact, that the storm of the 3rd was 
like that of the 2nd. The wind was due south at eight in the morning, 
then it became south-west, then west, and finally north-west, when the 
storm abated, because the collision between the two winds had occurred. — 
Comptes Rendus , lvii. No. 25. 
The Aerial Currents of the Globe.— Under the title of terrestrial physics, 
we notice an interesting resume of what is already known upon the sub- 
ject of atmospheric currents. This has been sketched out by M. Martin 
Saint-Leon, and is as follows : — The general circulation of the atmosphere 
is produced by the difference in temperature of different localities, and 
hence is modified by the seasons. At the equator, between the warmest 
and coldest periods of the year, the variation is slight, and, with a few 
exceptions of local origin, this variation increases with latitude. From this 
it follows that towards the end of the northern climatologic summer, the 
north-east inferior current is slackened, and towards the end of the winter 
is accelerated. This is doubtless the reason that, between the tropic of 
Cancer and the Equator, the autumn is invariably the hottest season, and 
the spring the coldest. The periodic colds of April in our climates may be 
attributed to the activity of the inferior north-east current. At Paris, the 
absorption of heat by the earth commences about the loth of January, but 
as we approach the poles this process is later. About the end of winter the 
inferior north-east current has increased in power, and constitutes a wave 
which passes over France towards the middle of April. The influences of 
lands and other local causes modify the direction of the inferior currents ; 
wind currents also in the neighbourhood of continental surfaces are often 
opposite in direction to the general movement. The subject of surface 
currents is one for the consideration of the navigator. The general inferior 
current is nearly 8,000 metres high, and its movements may be detected 
by watching the small white clouds called cirrhi, which travel with it. It 
is easy to conceive of the numerous advantages arising from this constant 
circulation of the atmosphere. The heated air is elevated ; it abandons its 
moisture on cooling, and gives it in the form of rain to the parched-up soil. 
At the same time the heat is distributed over other latitudes, instead of 
being allowed to accumulate at the Equator. — Vide Presse Scicntifique des 
deux Mondes f vol. 2, No. 22. 
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