Again, seeing I have supposed the moon to be carried about by the simple motion of the earth in the little circle _l b k c_; and demonstrated, at the 4th article of chapter XXI, that whatsoever is moved by a movent that hath simple motion, will be moved always with the same velocity; it follows, that the centre of the earth will be carried in the circumference _l b k c_ with the same velocity with which the moon is carried in the circumference _m n o p_. Wherefore the time, in which the moon is carried about in _m n o p_, is to the time, in which the earth is carried about in _l b k c_, as one circumference to the other, that is, as _a o_ to _a k_. But _a o_ is observed to be to the semidiameter of the earth as 59 to 1; and therefore the earth, if _a k_ be put for its semidiameter, will make fifty-nine revolutions in _l b k c_ in the time that the moon makes one monthly circuit in _m n o p_. But the moon makes her monthly circuit in little more than twenty-nine days. Wherefore the earth shall make its circuit in the circumference _l b k c_ in twelve hours and a little more, namely, about twenty-six minutes more; that is to say, it shall make two circuits in twenty-four hours and almost fifty-two minutes; which is observed to be the time between the high-water of one day and the high-water of the day following. Now the course of the waters being hindered by the southern part of America, their motion will be interrupted there; and consequently, they will be elevated in those places, and sink down again by their own weight, twice in the space of twenty-four hours and fifty-two minutes. And thus I have given a possible cause of the diurnal reciprocation of the ocean. Now from this swelling of the ocean in those parts of the earth, proceed the flowings and ebbings in the Atlantic, Spanish, British, and German seas; which though they have their set times, yet upon several shores they happen at several hours of the day. And they receive some augmentation from the north, by reason that the shores of China and Tartary, hindering the general course of the waters, make them swell there, and discharge themselves in part through the strait of Anian into the Northern Ocean, and so into the German Sea.