1And becauſe that in the years paſt I had occaſion by Order of
our Lord Pope Vrban 8. to apply my thoughts to the motion of
the Waters of Rivers, (a matter difficult, moſt important, and
little handled by others) having concerning the ſame obſerved
ſome particulars not well obſerved, or conſidered till now, but of
great moment both in publick and private affairs; I have thought
good to publiſh them, to the end that ingenious ſpirits might
have occaſion to diſcuſſe more exactly then hitherto hath been
done, ſo neceſſary and profitable a matter, and to ſupply alſo my
defects in this ſhort and difficult Tractate. Difficult I ſay, for
the truth is, theſe knowledges, though of things next our ſenſes,
are ſometimes more abſtruce and hidden, then the knowledge of
things more remote; and much better, and with greater exquiſit
neſs are known the motions of the Planets, and Periods of the
Stars, than thoſe of Rivers and Seas: As that ſingular light of
Philoſophie of our times, and my Maſter Signore Galileo Galilei
wiſely obſerveth in his Book concerning the Solar ſpots. And
to proceed with a due order in Sciences, I will take ſome ſuppo
ſitions and cognitions ſufficiently clear; from which I will after
wards proceed to the deducing of the principal concluſions. But
to the end that what I have written at the end of this diſcourſe in
a demonſtrative and Geometrical method, may alſo be under
ſtood of thoſe which never have applyed their thoughts to the
ſtudy of Geometry; I have endeavoured to explain my conceit
by an example, and with the conſideration of the natural things
themſelves, muſt after the ſame order in which I began to doubt
in this matter; and have placed this particular Treatiſe here in
the beginning, adverting nevertheleſs, that he who deſires more
full and abſolute ſolidity of Reaſons, may overpaſs this prefatory
diſcourſe, and onely conſider what is treated of in the demonſtra
tions placed towards the end, and return afterwards to the conſi
deration of the things collected in the Corollaries and Appendices;
which demonſtrations notwithſtanding, may be pretermitted by
him that hath not ſeen at leaſt the firſt ſix Books of the Elements
of Euclid; ſo that he diligently obſerveth that which fol
loweth.
our Lord Pope Vrban 8. to apply my thoughts to the motion of
the Waters of Rivers, (a matter difficult, moſt important, and
little handled by others) having concerning the ſame obſerved
ſome particulars not well obſerved, or conſidered till now, but of
great moment both in publick and private affairs; I have thought
good to publiſh them, to the end that ingenious ſpirits might
have occaſion to diſcuſſe more exactly then hitherto hath been
done, ſo neceſſary and profitable a matter, and to ſupply alſo my
defects in this ſhort and difficult Tractate. Difficult I ſay, for
the truth is, theſe knowledges, though of things next our ſenſes,
are ſometimes more abſtruce and hidden, then the knowledge of
things more remote; and much better, and with greater exquiſit
neſs are known the motions of the Planets, and Periods of the
Stars, than thoſe of Rivers and Seas: As that ſingular light of
Philoſophie of our times, and my Maſter Signore Galileo Galilei
wiſely obſerveth in his Book concerning the Solar ſpots. And
to proceed with a due order in Sciences, I will take ſome ſuppo
ſitions and cognitions ſufficiently clear; from which I will after
wards proceed to the deducing of the principal concluſions. But
to the end that what I have written at the end of this diſcourſe in
a demonſtrative and Geometrical method, may alſo be under
ſtood of thoſe which never have applyed their thoughts to the
ſtudy of Geometry; I have endeavoured to explain my conceit
by an example, and with the conſideration of the natural things
themſelves, muſt after the ſame order in which I began to doubt
in this matter; and have placed this particular Treatiſe here in
the beginning, adverting nevertheleſs, that he who deſires more
full and abſolute ſolidity of Reaſons, may overpaſs this prefatory
diſcourſe, and onely conſider what is treated of in the demonſtra
tions placed towards the end, and return afterwards to the conſi
deration of the things collected in the Corollaries and Appendices;
which demonſtrations notwithſtanding, may be pretermitted by
him that hath not ſeen at leaſt the firſt ſix Books of the Elements
of Euclid; ſo that he diligently obſerveth that which fol
loweth.
I ſay therefore, that having in times paſt, on divers occaſi
ons heard ſpeak of the meaſures of the waters of Rivers, and
Fountains, ſaying, ſuch a River is two or three thouſand feet of
water; ſuch a ſpring-water is twenty, thirty, or forty inches, &c.
Although in ſuch manner I have found all to treat thereof in
word and writing, without variety, and as we are wont to ſay,
conſtanti ſermone, yea even Artiſts and Ingeneers, as if it were
a thing that admitted not of any doubt, yet howſoever I re
mained ſtill infolded in ſuch an obſcurity, that I well knew I un
ons heard ſpeak of the meaſures of the waters of Rivers, and
Fountains, ſaying, ſuch a River is two or three thouſand feet of
water; ſuch a ſpring-water is twenty, thirty, or forty inches, &c.
Although in ſuch manner I have found all to treat thereof in
word and writing, without variety, and as we are wont to ſay,
conſtanti ſermone, yea even Artiſts and Ingeneers, as if it were
a thing that admitted not of any doubt, yet howſoever I re
mained ſtill infolded in ſuch an obſcurity, that I well knew I un
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