Chase.) ] 30 {May 18, 
a solid mathematical basis. Ie showed that, in the northern hemisphere, 
all moving bodies are constantly subjected, in consequence of the Harth’s 
rotation, to a deflection towards the right hand. Hence all atmospheric 
surface currents which are mainly governed by a downward pressure, tend 
to curve in the direction of the hands of a watch, or successively through 
north, east, south, west. All surface currents which are mainly governed 
by an upward pressure, tend to flow in an opposite direction, or through 
north, west, south, east.* The heavy winds are called anticyclonic ; the 
light winds, cyclonic. 
There can be no descending currents in one place without ascending 
currents in. another ; therefore, in every atmospheric disturbance, there 
must be simultaneous cyclonic and anticyclonic winds. Such disturb- 
ances originate either in an unusual cooling and condensation, or in an unus- 
ual heating and expansion of air. In the former case the inflow, in the 
upper regions of the atmosphere, will produce an increased pressure, In 
the latter, the outflow will produce a diminution of pressure. In the 
restoration of equilibrium, currents of warm air are often brought into 
contact. with colder currents. If the currents are both saturated with 
moisture, or if they contain more vapor than can be retained under the 
temperature of the mixed currents, precipitation takes place, in the form 
of rain, hail, or snow. This precipitation reduces the weight of the at- 
mospheric column and the barometer falis. Accordingly, there is a con- 
stantly increasing tendency to cyclonism about storm centres, and there 
has been a very prevalent disposition to look upon all storms as of cy- 
clonic origin. 
A little reflection, however, will show that the initial mixture of cur- 
rents may be due to either of the causes above mentioned ; either to the 
flow of warmer air into a cold depression at the top of the atmosphere, or 
to a flow of cold air, at the earth’s surface, towards a region of low baro- 
metric pressure. In the former case, the initial superficial currents are de- 
termined by a downward pressure, and they are, therefore, anticyclonic ; in 
the latter they are determined by an upward pressure and are cyclonic. 
A careful study of the weather maps shows that the heaviest rains and 
snows occur in advance of the centres of low barometric pressure, or in 
the rear of the centres of high barometric pressure. If storms began in 
the cyclonic currents, the reverse should be true; the greatest effect fol- 
lowing the low centre and preceding the high centre. 
The frequent failures of forecasts, during the past winter, seem to have 
been mainly due to a misinterpretation or a misconception of these facts, 
to which the writer first called attention in 1871. 
403. Study of Stormy Anticyclonism. 
Loomis’s discussions (Note 367) show the need of watching the develop- 
ment of storms at all stages, from the first indications of atmospheric 
“This will be evident, if we imagine ourselves to be lying in the current and 
facing the direction towards which the pressure tends, 
