Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 2.djvu/532

 1 [ § 3'] fugal, it will contribute to lengthen the f ace and time of the lib ration; by lengthening the pace, it increaes ' the eccentricity; and by lengthening the time of the lib ration, it prmlracts the time of the revolution to the apis, and caues what is improperly called a motion of the apis forward. But when the line of apides is moving to the quadratures, the external force in the apides, is at that time centripetal 5 which will contribute to horten the pace and time of lib ration; and by hortening the pace will thereby leffen the eccentricity, and by hortening the time of lib ration, will thereby contract the time of the revolution to the apis; and caue what is im# properly called a retrograde motion of the apis. I hall only add a few remarks, which ought to have been made in their proper places. A As to the motion of the Moon in the elliptic epicycle (page 9.) it hould have been mentioned, that there is no need of any accurate and perfect decription of the curve called an ellipis, it being only rg hew the elongation of the Moon; from the center of the epicycle; which doth not require any uch accurate def@fiPIiQ11=

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