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atmospheric pressure is reduced, and the barometer falls from 
ten at night until four in the morning, because aqueous vapour 
is then abstracted from the atmosphere ; — and that the 
barometer rises afterwards from four to ten in the day because 
fresh vapour is then sent into the atmosphere by solar heat. 
The movements of the barometer during these twelve hours 
are therefore stated to be results of varying vai^ovk pressure 
alone, without any disturbance being produced in the gaseous 
mass. But from ten in the morning until four in the afternoon 
the liberated heat of condensing vapour makes the gases in 
the locality lighter ; whilst from four in the afternoon until 
ten at night they are made heavier through abstraetion of heat 
from them by cloud evaporation, making the fall and rise of 
the barometer which then take place, effects of varying 
GASEOUS pressure. And the last named kind of changes, 
when sufficiently great, are asserted to cause all the important 
disturbances that occur in the atmosphere in every part of the 
world. 
