Salusbury, Thomas Mathematical collections and translations 1667
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7
passing by its extreamest parts, wherewith it communicateth with
the River; in which parts, the Torrent being measured, shall
have such a certain measure: but the River swelling and rising,
also those parts of the Torrent augment in greatnesse and mea­
sure, though the Torrent, in that instant, dis-imbogue no more
water than it did before: so that the River being swelled, we
are to consider two mouths of the same Torrent, one lesse be­
fore the rising, the other greater after the rising, which mouths
discharge equal quantities of water in equal times; therefore the
velocity by the lesser mouth shall be greater than the velocity by
the greater mouth; and thus the Torrent shall be retarded from
its ordinary course.

COROLLARIE V.

From which operation of Nature proceedeth another effect
worthy of consideration; and it is, that the course of the water
retarding, as hath been said in those ultimate parts of the Tor­
rent, if it shall happen that the Torrent grow torbid and mud­
dy, and its streame be retarded in such a degree, that it is not
able to carry away those minute grains of Earth, which com­
pose the muddinesse; in this case the Torrent shall clear away
the mud, and carry away the Sand at the bottome of its own
Chanel, in the extream parts of its mouth, which raised and
voided Sand, shall again afterwards be carried away, when the
River abating, the Torrent shall return to move with its primitive
velocity.

COROLLARIE VI.

Whilst it is demonstrated, that the same water hath different
measures in its Chanel or course, according as it varieth in
velocity; so that the measure of the water is alwayes greater, where
the velocity is lesser; and on the contrary, the measure lesser,
where the velocity is greater: from hence we may most ele­
gantly render the reason of the usual Proverb, Take heed of the
still waters: For that if we consider the self same water of a
River in those parts, wherein it is less swift, and thence called still
or smooth water, it shall be, of necessity, of greater measure
than in those parts, in which it is more swift, and therefore ordi­
narily shall be also more deep and dangerous for passengers;
whence it is well said, Take heed of the still Waters; and this
saying hath been since applied to things moral.