Raphael Semmes, Memoirs of Service Afloat During the War Between the States

[682] by the dotted line, which passes through the centre of the cir. Cle, the vortex, V, or calm spot, would travel. There should be calms, therefore, about the 65th parallel. In the southern half of the circle, or that portion of it between the vortex and the pole, easterly winds should prevail. Navigators between the parallels of 65° and 75°, speak of calms as the normal meteorological condition. All nature seems frozen to death, the winds included. Unfortunately, we have no reliable data for the parallels beyond, and do not know, therefore, whether easterly winds are the prevalent winds or not. It is probable, as we approached the pole, that we should find another calm. The winds, [see the arrows,] as they come hurrying along the circle, from its northern segment, bring with them an impetus toward the east, derived from the diurnal motion of the earth, on its axis. As these winds approach the pole, this velocity increases, in consequence of the diminishing diameter of the parallels. To illustrate. If a particle of air on the equator, having a velocity eastward of fifteen miles per hour—and this is the rate of the revolution of the earth on its axis— should be suddenly transported to a point, distant five miles from the pole, it would have sufficient velocity to carry it entirely around the pole in one hour. Here we have two forces acting in opposition to each other—the impetus of the wind toward the east, given to it by the diurnal motion of the earth,