TIDAL LANDS
CHAPTER I Tidal and Current Data
   Tidal phenomena may be expressed as the resultant of the forces of mutual attraction between the earth and its attendant heavenly bodies. This attraction is directly proportional to their respective masses and inversely as the square of their respective distances. For practical purposes the movements of the sun nd moon are the arbiters of tidal effect. The pull of the moon n the earth is rather more than double that of the sun, by reason >f its comparative proximity.
Springs and Neaps.—The speed of revolution of the earth ibout its axis is such that the moon during each twenty-four I lours occupies a period of about fifty minutes longer in reaching I he same meridian. Setting aside minor perturbations of lunar novement, the result of this inequality of travel is that the times >f high and low water lag some fifty minutes each day. This ction results in what is described as the “ priming” of the tide. The difference in height of the diurnal tides is due to the greater I ir less degree in which the attractions of the sun and moon are 1 n opposition. When the moon is in its first and last quarters, 1 r in quadrature, that is, when the positions of the sun and moon form a right angle with the earth-axis, the maximum r tardation of tidal force results. This is the condition of neap des. When the moon is at full and new the pull of sun and moon are in one and the resultant tidal lift is at its maximum, his is the condition of spring tides. Lunar full and change
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