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Proceedings of tlie Royal Society of Edinburgh. [Sess. 
pressure side of the warmer less dense air of the S.W. current. An insta- 
bility arises, the denser air tending to burst its way through the warmer air, 
with the result of sudden changes of direction and a squally character of 
the wind. 
On referring to fig. 1 (or fig. 2), it at once appears that the result of 
the principle just stated is to accelerate the mingling of dense air with the 
rarefied portion over A, and retard the outward movement of the relatively 
,o° 
, 01 ° 
denser air above and below. Thus air accumulates over A, the surface 
pressure is increased, and adiabatic compression raises the temperature of the 
lower portion, giving rise to a typical anticyclone, as shown in figs. 5 and 6. 
Similarly the air is expelled from the region of reduced entropy over C 
more rapidly than it enters the region of increased entropy, the result 
being the formation of a typical depression. The changes of temperature, 
pressure, density, and entropy are easily inferred from equations (l)-(5) by 
reasoning similar to that previously employed, and may be briefly de- 
scribed as a diminution in intensity of the changes above the level H=x, 
and an increase in pressure temperature and density, with but slight 
change of entropy, at lower levels. The deviations at different levels from 
