§ 789. STORMS, HURRICANES, AND TYPHOONS. 421 



station,' a' a' a\ when the storm commenced, and the arrows d! 

 a' the direction afterward, thus showing it to have veered against 

 the hands of a watch. And this is the direction in which the 

 forces of diurnal rotation, when not mastered by opposing forces, 

 always require the wind, when not blowing round in spirals and 

 a whirl, to haul in the southern hemisphere. Now, paradoxical 

 as it may at first seem, it is also the forces of diurnal rotation that 

 give that same wind, when it is blowing round in spirals, its first 

 impulse to march round in the contrary direction, or with the 

 hands of a watch; but this is as it should be — it hauls one way, 

 and marches the other. After passing a, and each of the other 

 stations, a' a\ the rush of wind is sufiicient, let us suppose, to 

 create a whirl. The wind at a' a' a\ continuing on with a cir- 

 cular motion, is represented thenceforward in its course by the 

 curved arrows a e, a' e. The wind coming from the east and the 

 west has no direct impulse from diurnal rotation, but the wind on 

 either side of it has, and hence the prime vertical wind is carried 

 around with the rest. If, now, we imagine the disc C to be put 

 in motion, and the storm to become a traveling one, we shall have 

 to consider the composition and resolution of other forces also, 

 such as those of traction, aberration, and the like, before we can 

 resolve the whirlwind. 



789. But the cyclonologists do not locate their storms in such 

 Bernouiui's formula, high latitudes as the parallels of Cape Horn. Ilence 

 we might safely infer, one would suppose, that in high southern 

 latitudes a north wind has a tendency to incline to the westward 

 and a south wind to the eastward ; and the cause of this tendency 

 is in operation, whether the place of low barometer be a disc or 

 an oblong, for it is in obedience to the trade-wind law, as ex- 

 pounded by Halley, that it so operates; and it will also be the 

 case whether the wind be caused by an influx into the place of 

 low, or the efflux from the place of high barometer ; or, as is 

 generally the case, by both together. If the distance between 

 the place of high and low barometer were always the same, then 

 a given difference of barometric pressure would always be follow- 

 ed by a wind of the same force or velocity. By expanding Ber- 

 nouilli's formula for the velocity of gas jets under given press- 

 ures. Sir John F. W. Herschel has computed* the velocity and the 



* See article Meteorology, Encyclopedia Britannica, 1857. 



