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asymmetric distribution of oceans and continents, and thus the large centers of action are formed.It is finally shown, through a study of weekly mean pressure-charts, that the dimensions and movements of the centers of action conform fairly well to the theoretically determined flowpattern characteristics. U. S. Weather Bureau, Washington, D. C ATMOSPHERIC DISTURBANCES ON THE ROTATING EARTH B. HaurwitzIn a pressure-field with low pressure to the north, high pressure to the south on which a sinusoidal disturbance is superimposed, more air is transported between consecutive Isobars in lower than in higher latitudes. This follows from the geostrophlc wind-relation which contains the sine of the latitude in the denominator. Thus, more air flows across the pressure-trough lines than across the wedge-lines. Divergence occurs east of the wedge-lines, convergence to the west and the disturbance moves towards the west provided that the effect of divergence and convergence is greater than the zonal gradient wind-velocity. This effect of the latitudinal variation of the Coriolis force has been studied by Rossby [see 1 of "References at end of pa per). He assumes for the sake of simplicity that the lateral extent of the disturbance--that is, its width perpendicular to the direction of motion--is infinite. In reality the width of the disturbance is finite. The effect of convergence and divergence is smaller than in the case of infinite width since the amplitude of the disturbance and consequently the effect of the latitudinal variation of the Coriolis force decrease toward the boundaries of the disturbance and since the isobars are not equidistant any longer. This is borne out by the theory [2]. When wave-length, width of the disturbance, and zonal gradient wind-velocity are in a certain relation to each other, the perturbation is stationary. Figure 1 shows this relation graphical ly. The ordinate is the width of the disturbance, the abscissa is the zonal wind-velocity. Since the relation depends also on the latitude, tnree different velocity-scales are given cor responding to latitudes 60°, 45°, and 30°. The curves plotted are lines of equal stationary wave-length. If the wave-lengths were unaffected by the width of the perturbations, the curves would be parallel to the ordinate axis. Especially the curves for longer waves show olearly the effect of the finite width of the disturbances.

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