Archimedes Texts

394

nesse of the Vessel, in its acquiring in several hours of the day
several degrees of velocity, they are with very little difference
acquired by all its parts; for as well the precedent as the subse
quent, that is to say, both the Eastern and Western parts, do
accelerate and retard almost in the same manner; and withal
making that alteration by little and little, and not by giving the
motion of the conteining Vessel a sudden check, and retard
ment, or a sudden and great impulse or acceleration; both it
and all its parts, come to be gently and equally impressed with
the same degrees of velocity; from which uniformity it follow
eth, that also the conteined water with but small resistance and
opposition, receiveth the same impressions, and by consequence
doth give but very obscure signes of its rising or falling, or of its
running towards one part or another. The which effect is likewise
manifestly to be seen in the little artificial Vessels, wherein the
contained water doth receive the self same impressions of veloci
ty; when ever the acceleration and retardation is made by gentle
and uniform proportion. But in the Straights and Bays that for a
great length distend themselves from East to West, the accele
ration and retardation is more notable and more uneven, for
that one of its extreams shall be much retarded in motion, and
the other shall at the same time move very swiftly: The reci
procal libration or levelling of the water proceeding from the im
petus that it had conceived from the motion of its container.
The which libration, as hath been noted, hath its undulations
very frequent in small Vessels; from whence ensues, that though
there do reside in the Terrestrial motions the cause of confer
ring on the waters a motion onely from twelve hours to twelve
hours, for that the motion of the conteining Vessels do ex
treamly accelerate and extreamly retard but once every day,
and no more; yet neverthelesse this same second cause depend
ing on the gravity of the water which striveth to reduce it self to
equilibration, and that according to the shortnesse of the Ves
sel hath its reciprocations of one, two, three, or more hours, this
intermixing with the first, which also it self in small Vessels is
very little, it becommeth upon the whole altogether insensible.
For the primary cause, which hath the periods of twelve hours,
having not made an end of imprinting the precedent commoti
on, it is overtaken and opposed by the other second, depen
dant on the waters own weight, which according to the brevity
and profundity of the Vessel, hath the time of its undulations of
one, two, three, four, or more hours; and this contending
with the other former one, disturbeth and removeth it, not per
mitting it to come to the height, no nor to the half of its moti
on; and by this contestation the evidence of the ebbing and