much concerned to heed it , whereof more will be faid by and 
&y ; ) that wefhouW rather affign the beginnings of February 
and November^ thm ih^ two jEquinexes, 
Now in order to the giving account of thefe three Periods, 
aeoDitding to the Lams of ' Mmm and Mechanic^ frtmiples ^ We 
fhall/r/^cake for granted, what is now adayes pretcy commonly 
ei^itertained by thofe , who treat of fuch matters » T^dt a Body 
in motion is apt to continue its motion ^ and that in the fame degree of 
celerity, unlefs hindred by fome contrary Impediment ; ( like as a Bo- 
dy.atreft, to continue fQ/kialefs by fome fufEcientmoverj put 
into motion: ) And accordingly (which daily experience te- 
ftifies ) if on a Board or Table, fome loofe incumbent weight, 
be for fome time moved, ^ have thereby contra^ed an Impetus 
to motion at fuch a rate ; if that Board or Table chance by 
fome external obftacle, or otherwife, to be (topped or confide- 
rably retarded in its motion , the incumbent loofe Body will 
llioot forward upon it : And contrary wvfejin cafe that Board or 
Table chance to be accelerated or put forward with aconfide- 
rably greater fpeed than before,the loofe incumbent Body,(not 
having yet obtained an eqiiaMmpetus with it ^ will be left be- 
hind,or feem to fly backward upon it. Or, (which is Galilao's 
inftance,) if a broad VefTel of Water , fot fome rim> evenly 
carried forward with the water in it, chance to meet wittj a fl:op, 
or to flack its motion,the Water will dafli forward and rife high- 
er at the fore part of the VeiTel : AndjContrarywifejif .the Vef- 
fel be fuddenly put for^vard fafter than before , the Water will 
dafli backwards, and rife at the hinder part of the V'effc^l. So 
th^tr an Acceleration or Retardation of the VefTel , which car- 
ries it, will canfe a rifing of the Water in one part, anda fal'ing 
in another : ( which yet, by its own weight, will again be redu- 
ced to a Level as it was before J Andconfequently,^fuppofing 
the S-a to be but as a loofe Body, carried about with the Eart!h, 
but not fo united to it, as ncceffarily 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 , wi-il 
caufe ( more or lefs, according to the proportion of it ) fuch a 
dufliing of the Water, or rifing at one part, with a Falling at 
another5as is that^which we call the Flux and Reflux of the Sea.- 
Now 
