188 What are Cyclones ? 
United States. It is believed, however, that the clew to these 
cases is already afforded ; and that many or most of these storms 
were true cyclones; with orbital courses really analogous to those 
which are seen on the Chart. 
Wuar are Cyctones?—The term Cyclone was first proposed 
by Mr. Piddington, to designate any considerable extent or area 
of wind which exhibits a turning or revolving motion ; without 
regard to its varying velocity, or to the different names which are 
often applied to such winds. If used in this sense it may pre- 
vent the confusion which often results from other names, more 
variable or indeterminate in their signification. Thus, all hurr- 
canes or violent storms may perhaps be considered as cyclones oF 
revolving winds. But it by no means follows that all cyclones 
are either hurricanes, gales, or storms. For the word is not de- 
signed to express the degree of activity or force, which may be 
manifested in the moving disk or stratum of rotating atmosphere 
to which it is applied. It often designates light and feeble winds, 
as well as those which are strong and violent.* es 
It follows that the local directions and changes of the wind in 
any cyclone, and their effect on the barometer, are much like 
those exhibited in the gales and storms of the same region, €X- 
cept in the degree of their effect ; which is doubtless proportioned 
to the general activity of the rotation, integrally considered. 
The cyclones are often productive of rain in a portion of the 
cyclonic area; but vary in this respect, in different regions, and 
at different seasons of the year. 1b ae 
Universauity or Cyciones,—As early as 1833 my inquitles 
led me to announce the conclusion that the ordinary routine of 
the winds and weather in these latitudes often corresponds to the 
phases which are exhibited in the revolving storms, already de- 
from estern board to some point on the eastern side of the meridian, a. 
panied and often preceded by a fall of the barometer, On the right margin ° 
yclon rom the southeasterD quar 
to the northwestern, with a falling barometer; and when the axis of the lhe or 
passed, its later winds are found crossing the line of progress in the opposite 
i e southeastern, with a rising barcne al 
The true cyclonic wind may not always be found at the earth’s surface, 1 ©” 
ities of direction are often noticed at the surface; but i S feet, ext 
monk pens that the storm-scud, at the elevation of a few hundred feet, € 
only uP. ; P the of direction suc 
cessively observed in the storm-scud, are commonly in advance of those in the “sig 
est wind, 
