132 THE JOURNAL Or GEOLOGY. 
clouds in the rear; barometer falling in front, rising in the 
rear. It should also be remembered that a change in intensity 
or direction, may cause the barometer to fall in the .cyclone’s 
rear, or rise in its front, and that any change in direction or force 
of wind, or in character of cloud, is generally accompanied by a 
change in gradient. 
In the descending eddy, or anticyclone, the conditions are 
just reversed. As the descending aii nears, the suptaceomnthieas 
earth, it slides off horizontally, flowing away from the center in 
all directions, with a spiral movement; hence as the progressive 
motion of the anticyclone is from west to east—a west wina 
must be tts herald and an east wind mark its rear. As the air from 
the colder upper regions settles toward the warmer earth there 
will be little tendency to form clouds, except those of the pure 
stratus type. In fact this is the only type of cloud which can 
occur in a typical anticyclone as defined above, but for reasons 
that will be explained further on, both cumulus and feathery 
cirrus clouds do occur in most anticyclonic areas. The down- 
ward motion of the air increases its apparent weight and so the 
barometer rises in tts front and falls in tts rear. Anticyclones are 
also subject to changes in intensity and direction similar to 
those which occur in cyclonic areas. 
The characteristics of the anticyclone are: wind from some 
westerly point in front, becoming easterly in the rear; generally 
a clear sky, with perhaps a few cumulus clouds in front, and 
cirrus in the rear; rarely the whole sky becomes dull and leaden 
from the formation of pure stratus clouds; barometer rising in 
front, falling in the rear. 
For our present purpose we may assume that the entire 
atmosphere is made up of such cyclonic and anticyclonic areas, 
in fact the assumption is not far from the truth in this latitude, 
and as each floats over us, it causes the index of our barometer 
to move upward or downward, the extremes covering an arc that 
represents nearly three thousand feet of elevation. From this 
it will be seen how fruitful a source of error these atmospheric 
configurations may be, and how essential it is for anyone who 
