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draw this fluid out into the form of an ellipsoid, of which the long diameter would be turned toward the moon. But the earth itself, being solid, cannot be drawn out into this shape, while the ocean, being fluid, is thus drawn out. The result is that we have high tides at the two ends of the ellipse into which the ocean is drawn, and low tides in the mid-region.

The complete explanation of the subject requires a statement of the laws of motion which cannot be made

here. I will, however, remark that if the attraction of the moon on the earth were always in the same direction, the two bodies would be drawn together in a few days. But owing to the revolution of the moon round the earth the direction of the pull is always changing, so that the earth is, in the course of a month, only drawn about three thousand miles from its mean position by the moon's pull.

It might be supposed that if the moon produces the tides in this way we should always have high tide when the moon is on the meridian and low tide when the moon is in the horizon. But such is not the case, for two reasons. In the first place it takes time for the moon to draw