1the River, in ſuch a caſe there muſt follow very great and irre
pable innundations.
pable innundations.
COROLLARIE X.
From what hath been demonſtrated, we may with facility re
ſolve the doubt which hath troubled, and ſtill poſeth the moſt
diligent, but incautelous obſervers of Rivers, who meaſuring
the Streams and Torrents which fall into another River; as thoſe
for inſtance, which enter into the Po, or thoſe which fall into Ti
ber; and having ſummed the total of theſe meaſures, and con
ferring the meaſures of the Rivers and Brooks, which fall into
Tiber, with the meaſure of Tiber, and the meaſures of thoſe which
diſimbogue into Po, with the meaſure of Po, they find them not
equal, as, it ſeems to them, they ought to be, and this is becauſe
they have not well noted the moſt important point of the varia
tion of velocity, and how that it is the moſt potent cauſe of won
derfully altering the meaſures of running Waters; but we moſt
facilly reſolving the doubt, may ſay that theſe Waters diminiſh
the meaſure, being once entered the principal Channel, becauſe
they increaſe in velocity.
ſolve the doubt which hath troubled, and ſtill poſeth the moſt
diligent, but incautelous obſervers of Rivers, who meaſuring
the Streams and Torrents which fall into another River; as thoſe
for inſtance, which enter into the Po, or thoſe which fall into Ti
ber; and having ſummed the total of theſe meaſures, and con
ferring the meaſures of the Rivers and Brooks, which fall into
Tiber, with the meaſure of Tiber, and the meaſures of thoſe which
diſimbogue into Po, with the meaſure of Po, they find them not
equal, as, it ſeems to them, they ought to be, and this is becauſe
they have not well noted the moſt important point of the varia
tion of velocity, and how that it is the moſt potent cauſe of won
derfully altering the meaſures of running Waters; but we moſt
facilly reſolving the doubt, may ſay that theſe Waters diminiſh
the meaſure, being once entered the principal Channel, becauſe
they increaſe in velocity.
COROLLARIE XI.
Through the ignorance of the force of the velocity of the Wa
ter, in altering its meaſure, & augmenting it when the velocity
diminiſheth; and diminiſhing it when the velocity augmenteth:
The Architect Giovanni Fontana, endeavoured to meaſure, and
and to cauſe to be meaſured by his Nephew, all the Brooks and
Rivers which diſcharged their Waters into Tiber, at the time of
the Innundation; which happened at Rome in the year 1598,
and publiſhed a ſmall Treatiſe thereof, wherein he ſummeth up
the meaſures of the extraordinary Water which fell into Tiber,
and made account that it was about five hundred Ells more than
ordinary; and in the end of that Treatiſe concludeth, that to re
move the Innundation wholly from Rome, it would be neceſſary
to make two other Channels, equal to that at preſent, and that
leſſe would not ſuffice; and finding afterwards that the whole
Stream paſſed under the Bridge Quattro-Capi, (the Arch where
of is of a far leſs meaſure then five hundred Ells) concludeth,
that under the ſaid Bridge paſt a hundred fifty one Ells of Water
compreſſed, (I have ſet down the preciſe term of compreſt Wa
ter, written by Fontana) wherein I finde many errors.
ter, in altering its meaſure, & augmenting it when the velocity
diminiſheth; and diminiſhing it when the velocity augmenteth:
The Architect Giovanni Fontana, endeavoured to meaſure, and
and to cauſe to be meaſured by his Nephew, all the Brooks and
Rivers which diſcharged their Waters into Tiber, at the time of
the Innundation; which happened at Rome in the year 1598,
and publiſhed a ſmall Treatiſe thereof, wherein he ſummeth up
the meaſures of the extraordinary Water which fell into Tiber,
and made account that it was about five hundred Ells more than
ordinary; and in the end of that Treatiſe concludeth, that to re
move the Innundation wholly from Rome, it would be neceſſary
to make two other Channels, equal to that at preſent, and that
leſſe would not ſuffice; and finding afterwards that the whole
Stream paſſed under the Bridge Quattro-Capi, (the Arch where
of is of a far leſs meaſure then five hundred Ells) concludeth,
that under the ſaid Bridge paſt a hundred fifty one Ells of Water
compreſſed, (I have ſet down the preciſe term of compreſt Wa
ter, written by Fontana) wherein I finde many errors.
The firſt of which is to think that the meaſures of theſe Wa
ters compreſſed in the Channels of thoſe Brooks and Rivers,
ters compreſſed in the Channels of thoſe Brooks and Rivers,
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