much concerned to Heed it , whereof more will be faid by and 
by ; ) that we fhould rather affign the beginnings of February 
and November, than the two /Equinoxes* 
Now in order to the giving account of thefe three periods, 
according to the Laws of Motion and Mechanic^ Principles * We 
(lull fr(l cake for granted, what is now adayes pretty commonly 
entertained by thofe , who treat of fuch matters 5 That a Body 
in motion is apt to continue its motion , and that in the fame degree of 
celerity , tmlefs kindred by fome contrary Impediment j ( like as a Bo- 
dy at reft, to continue To, unlefs by fome fufficient mover, put 
into motion:) And accordingly (which daily experience te- 
'(bfids ) if on a Board or Table, fome loofe incumbent weight, 
be for fome rime moved, & have thereby contracted an Impetus 
to motion at fuch a rate » if that Board or Table chance by 
fome external obftacle, or otherwife, to be flopped or confide- 
rably retarded in its motion , the incumbent loofe. Body will 
flioot forward upon it: And contrary wife, in cafe that Board or 
Table chance to be accelerated or put forward with a confide- 
rably greater fpeed than before, the loofe incumbent Body, (not 
having yet obtained an equal Impetus with it ) will be leftbe- 
hindjOr feem to fly backward upon it. Or, (which is Galilms 
in fiance,) if abroad V efTei of Water , for fome time evenly 
carried forward with the water in it, chance to meet with a ftop, 
or to flack its motion^he Water will dafh forward and rife high- 
er at the fore part of the VefTei : And,eontracywife,if the Vef- 
fel be fuddenly put forward falter tlran before ^ the W ater will 
dafh backwards, and rife at the hinder part of the VefTei. So 
that an Acceleration or Retardation of tjie VefTei , which car- 
ries it, will caufe a rifingof the Water in one part, and a falling 
in another : ( which yet, by its own weight, will again be redu- 
ced to a Level as it was before.) And confequently, fuppofing 
the Sea to be but as a loofe Body, carried about with the Earth, 
but not fo united to it, as necefTarily to receive the fame degree 
of Impetus with it, as its fixed parts do ; The acceleration or re- 
tardation in the motion of this or that part of the Earth , will 
caufe ( more or lefs, according to the proportion of it ) fuch a 
dafhing of the Water, or rifing at one part, with aFallingat 
another, as is that, which we call the Flux and Reflux of the Sea: 
Now 
