Castelli, Benedetto, Of the mensuration of running waters, 1661

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1do think that it is abſolutely impoſſible to make this enquiry, and
will ſay unto me, Quis menſus eſt pugillo aquas, & terram palmo
ponderavit?
Yet nevertheleſs I will propound a way whereby,
at leaſt in groſs, one may find out the ſame.
Take a Veſſel of Cylindrical Figure, holding two barrels of
water, or thereabouts; and then fill it with the water of Brent,
at its Mouth or Fall into the Lake; but in the Lake at the time
that the Brent runneth muddy, and after it hath begun to run
muddy for eight or ten hours, to give the mud time to go as far
as S. Nicolo, to iſſue into the Sea; and at the ſame time take
another Veſſel, like, and equal to the firſt, and fill it with the wa­
ter of the Lake towards S. Nicolo, (but take notice that this ope­
ration ought to be made at the time when the waters go out,
and when the Sea is calm) and then, when the waters ſhall have
ſetled in the aforeſaid Veſſels, take out the clear water, and con­
ſider the quantity of Sand that remains behind, and let it be ſet
down, or kept in mind: And I am eaſily induced to think, that
that ſhall be a greater quantity of Sand which ſhall be left in the
firſt Veſſel, than that left in the ſecond Veſſel.
Afterwards
when the Brent ſhall come to be clear, let both the operations be
repeated, and obſerve the quantity of Sand in the aforeſaid Veſ­
ſels; for if the Sand in the firſt Veſſel ſhould be moſt, it would
be a ſign, that in the revolution of a year the Brent would depoſe
Sand in the Lake: And in this manner one may calculate to a
ſmall matter what proportion the Sand that entreth into the Lake,
hath to that which remains: And by that proportion one may
judge how expedient it ſhall be for publick benefit.
And if at
ſeveral times of the year you carefully repeat the ſame operati­
ons, or rather obſervations, you would come to a more exact
knowledge in this buſineſs: And it would be good to make the
ſaid operations at thoſe times, when the Lake is diſturbed by
ſtrong high Winds, and made muddy by its own Mud, raiſed by
the commotion of the Waters.
This notion would give us great light, if the ſame obſervations
ſhould be made towards the Mouth of Lio, at ſuch time as the
waters flow and ebb, in calm ſeaſons; for ſo one ſhould come to
know whether the waters of the Lake are more thick at the going
out, than at the entrance.
I have propounded the foregoing
way of meaſuring Sands and Mud, to ſhew that we are not ſo
generally, and inconſiderately to pronounce any ſentence, but
proceed to ſtricter inquiries, and then deliberate what ſhall be
moſt expedient to be done.
Others may propoſe more exqui­
ſite examinations, but this ſhall ſerve me for the preſent.
I will add onely, that if any one had greater curioſity (it would
be profitable to have it) in inveſtigating more exactly the quan­

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