Salusbury, Thomas Mathematical collections and translations 1667
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408
consisteth the original cause of the irregular motion of the Ves­
sels, and consequently of the Ebbing and Flowing: insomuch

that if these additions and substractions should alwayes proceed
in the same proportion, in respect of the Annual motion, the
cause of the Ebbing and Flowing would indeed continue, but
yet so as that they would perpetually return in the self same man­
ner: But we are to finde out the cause of making the same Eb­
bings and Flowings in divers times greater and lesser: There­
fore we must (if we will retain the identity of the cause) find the
alteration in these additions and substractions, that make them
more & less potent, in producing those effects which depend there­
upon. But I see not how that potency and impotence can be intro­
duced, unlesse by making the same additions and substractions,
one while greater, and another while lesser; so that the accelera­
tion and the retardment of the compound motion, may be made,
sometimes in greater, and sometimes in lesser proportion.

The alterations
in the effects argue
alteration in the
cause.

The causes at
large assigned of
the Periods Mo­
nethly and Annu­
al of the ebbing
and flowing.

The monethly
and annual altera­
tions of the tide can
depend upon no­
thing, save on the
alteration of the
additions & sub­
stractions of the
diurnal period from
the annual.

SAGR. I feel my self very gently led, as it were, by the hand,
and though I finde no rubs in the way, yet neverthelesse, like a
blind man, I see not whether your Clue leadeth me, nor can I
imagine where such a Journey will end.

SALV. Though there be a great difference between my slow
pac't Philosophy, and your more nimble Reason, yet neverthe­
lesse, in this particular which we are now upon, I do not much
wonder, if the apprehensivenesse of your wit be a little obscu­
red by the dark and thick mist that hides the mark, at which we
aime: and that which lesseneth my admiration is, the remem­
brance of the many hours, many dayes, yea more, many nights
that I have consumed in this contemplation, and of the many
times that, despairing to bring it to a period, I have, for an in­
couragement of my self, indeavoured to believe, by the exam­
ple of the unfortunate Orlando, that that might not possibly be
true, which yet the testimony of so many credible men set be­
fore my eyes: wonder not, therefore, if this once, contrary to
your custome, you do not foresee what I intend: and if you will
needs admire, I believe that the event, as far as I can judge un­
expected, will make you cease your wonderment.

SAGR. I thank God, that he did not permit that desperation
of yours to end in the Exit that is fabled of the miserable Or­
lando, nor in that which haply is no lesse fabulously related of
Aristotle,, that so neither my self nor others should be deprived
of the discovery of a thing, as abstruse as it was desirable: I
beseech you, therefore, to satisfie my eager appetite as soon as
you can.

SALV. I am ready to serve you: We were upon an inquiry
in what manner the additions and substractions of the Terrestri­