Another result of the path of a cyclone is that the direction of its center from the stand-point of any observer is readily known. A glance at the diagram shows at once that if any one within the storm area of a cyclone of the northern hemisphere stands with his back to the wind, the storm center, where the barometer is lowest, is invariably on his left: but if he stand with his back to the wind of a southern cyclone, the storm center is always on his right. Hence, if a vessel be overtaken by a cyclone, the captain at once may know how to pass beyond its range, by shaping his course at right angles to that of the wind. Thus, if in a northern cyclone, he must sail to the right, supposing his back is to the wind: in the southern hemisphere, he would sail to the left. As an example of the expansion of the storm area in its journey, may be mentioned the West India hurricane of 1839, which had, in the Antilles, a diameter of three hundred miles, which increased to five hundred at the Bermudas, and eight hundred on the parallel of 50° north latitude. To draw again upon the illustration of the spinning top, it will be observed that the curvilinear motion is extremely slow in comparison with that of rotation, but increases as the rotation decreases. The same law applies to the movement of cyclones. The slowest motion forward is usually near the apex of the curve: and the progress on the ocean is much slower than on the land. Traveling over the latter, the irregularities of surface act in the case of the storm just as a rough surface does in the case of the top. The motion may be accelerated, but its regularity is lessened. So while at sea the parabolic path of the storm is almost absolutely perfect, but on reaching the land its motion is more rapid, and less regular, conforming somewhat to the configuration of the surface.