Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 2.djvu/470

 6 ]. founded on a physical cause; and thoe are what relate to the fearing of the m¢an motions. For altho' it be of lit? tie or no ue in Astronomy to know the rules for acertaining the mean motions of the Node or Apogee, ince the faéi is all that is wanting, and that is othere wife known by comparing the observations of former ages with those of the present; yet in matter of peculation, this is the chief and rnofl nece£ fary thing required: ince there is no other way to know that the cause is rightly assigned, but by 'showing that the motions are o much and no more than what they ought to be. i i But that it may not be altogether without its —ue, I have added all the rules for the equation of the Moon's motion, except two; one of which is a monthly equation of the variation depending on the Moon's anomaly; and the other an equation arising from the Earth's being not in the focus of the Moon's orbit, as it has been uppoed to be, in all the modern theories ince Horrax. F or not having had time to examine over the obervations which are necessary, but being oblig'd inflcad thereof; to take Sir .I/imr: Ne¢wz'on's theory for tny  guide and direction, I cannot vnwfs