Salusbury, Thomas, Mathematical collections and translations (Tome I), 1667
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1flowing is wholly annihilated, or at leaſt very much obſcured.
I paſſe by the continual alteration of the air, which diſquieting
the water, permits us not to come to a certainty, whether any,
though but ſmall, encreaſe or abatement of half an inch, or
leſſe, do reſide in the Straights, or receptacles of water not
bove a degree or two in length.
Reaſons
ed of the
lar accidents
ſerved in the
bings and flowings.
Second cauſes
why in ſmall Seas
and in Lakes there
are no ebbings and
flowings.
I come in the ſecond place to reſolve the queſtion, why, there

not reſiding any vertue in the primary principle of commoving
the waters, ſave onely every twelve hours, that is to ſay, once
by the greateſt velocity, and once by the greateſt tardity of
motion; the ebbings and flowings ſhould yet nevertheleſſe
pear to be every ſix hours.
To which is anſwered, that this
termination cannot any wayes be taken from the primary cauſe
onely; but there is a neceſſity of introducing the ſecondary
ſes, as namely the greater or leſſe length of the Veſſels, and
the greater or leſſe depth of the waters in them conteined.
Which cauſes although they have not any operation in the
ons of the waters, thoſe operations belonging to the ſole
ry cauſe, without which no ebbing or flowing would happen,
yet nevertheleſſe they have a principal ſhare in determining the
times or periods of the reciprocations, and herein their
ence is ſo powerful, that the primary cauſe muſt of force give
way unto them.
The period of ſix hours therefore is no more
proper or natural than thoſe of other intervals of times, though
indeed its the moſt obſerved, as agreeing with our Mediterrane,
which was the onely Sea that for many Ages was navigated:
though neither is that period obſerved in all its parts; for
that in ſome more anguſt places, ſuch as are the
ſpont, and the Ægean Sea, the periods are much ſhorter,
and alſo very divers amongſt themſelves; for which
ſities, and their cauſes incomprehenſible to Ariſtotle, ſome
ſay, that after he had a long time obſerved it upon ſome
cliffes of Negropont, being brought to deſperation, he threw
himſelf into the adjoyning Euripus, and voluntarily drowned
himſelf.
The reaſon
ven, why the
bings and flowings,
for the moſt part,
are every ſix
hours.
In the third place we have the reaſon ready at hand, whence

it commeth to paſſe, that ſome Seas, although very long, as is
the Red Sea, are almoſt altogether exempt from Tides, which
happeneth becauſe their length extendeth not from Eaſt to
Weſt, but rather tranſverſly from the Southeaſt to the
weſt; but the motions of the Earth going from Weſt to Eaſt;
the impulſes of the water, by that means, alwayes happen to fall
in the Meridians, and do not move from parallel to parallel;
inſomuch that in the Seas that extend themſelves athwart
wards the Poles, and that the contrary way are narrow, there is

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