LEMMA.
That the Moments or Velocities of the ſame Moveable are different
upon different Inclinations of Planes, and the greateſt is by the
Line elevated perpendicularly above the Horizon, and by the
others inclined, the ſaid Velocity diminiſheth according as they
more and more depart from Perpendicularity, that is, as they in
cline more obliquely: ſo that the Impetus, Talent, Energy, or, we
may ſay, Moment of deſcending is diminiſhed in the Moveable by
the ſubjected Plane, upon which the ſaid Moveable lyeth and
deſcendeth.
upon different Inclinations of Planes, and the greateſt is by the
Line elevated perpendicularly above the Horizon, and by the
others inclined, the ſaid Velocity diminiſheth according as they
more and more depart from Perpendicularity, that is, as they in
cline more obliquely: ſo that the Impetus, Talent, Energy, or, we
may ſay, Moment of deſcending is diminiſhed in the Moveable by
the ſubjected Plane, upon which the ſaid Moveable lyeth and
deſcendeth.
And the better to expreſs my ſelf, let the Line A B be perpen
dicularly erected upon the Horizon A C: then ſuppoſe the
ſame to be declined in ſundry Inclinations towards the Horizon, as
in A D, A E, A F, &c. I ſay, that the greateſt and total Impetus
of the Grave Body in deſcending is along the Perpendicular B A,
and leſs than that along D A,
87[Figure 87]
and yet leſs along E A; and
ſucceſſively diminiſhing along
the more inclined F A, and fi
nally is wholly extinct in the
Horizontal C A, where the
Moveable is indifferent either
to Motion or Reſt, and hath not
of it ſelf any Inclination to
move one way or other, nor yet
any Reſiſtance to its being mo
ved: for as it is impoſſi
ble that a Grave Body, or a
Compound thereof ſhould move naturally upwards, receding from
the Common Center, towards which all Grave Matters conſpire
to go, ſo it is impoſſible that it do ſpontaneouſly move, unleſs
with that Motion its particular Center of Gravity do acquire Proxi
mity to the ſaid Common Center: ſo that upon the Horizontal
which here is underſtood to be a Superficies equidiſtant from the
ſaid Center, and therefore altogether void of Inclination, the Im
petus or Moment of that ſame Moveable ſhall be nothing at all.
Having underſtood this mutation of Impetus, I am to explain that
which, in an old Treatiſe of the Mechanicks, written heretofore
in Padona by our Academick, only for the uſe of his Scholars, was
diffuſely and demonſtratively proved, upon the occaſion of con
ſidering the Original and Nature of the admirable Inſtrument cal
led the Screw, and it is, With what proportion that mutation of
dicularly erected upon the Horizon A C: then ſuppoſe the
ſame to be declined in ſundry Inclinations towards the Horizon, as
in A D, A E, A F, &c. I ſay, that the greateſt and total Impetus
of the Grave Body in deſcending is along the Perpendicular B A,
and leſs than that along D A,
87[Figure 87]and yet leſs along E A; and
ſucceſſively diminiſhing along
the more inclined F A, and fi
nally is wholly extinct in the
Horizontal C A, where the
Moveable is indifferent either
to Motion or Reſt, and hath not
of it ſelf any Inclination to
move one way or other, nor yet
any Reſiſtance to its being mo
ved: for as it is impoſſi
ble that a Grave Body, or a
Compound thereof ſhould move naturally upwards, receding from
the Common Center, towards which all Grave Matters conſpire
to go, ſo it is impoſſible that it do ſpontaneouſly move, unleſs
with that Motion its particular Center of Gravity do acquire Proxi
mity to the ſaid Common Center: ſo that upon the Horizontal
which here is underſtood to be a Superficies equidiſtant from the
ſaid Center, and therefore altogether void of Inclination, the Im
petus or Moment of that ſame Moveable ſhall be nothing at all.
Having underſtood this mutation of Impetus, I am to explain that
which, in an old Treatiſe of the Mechanicks, written heretofore
in Padona by our Academick, only for the uſe of his Scholars, was
diffuſely and demonſtratively proved, upon the occaſion of con
ſidering the Original and Nature of the admirable Inſtrument cal
led the Screw, and it is, With what proportion that mutation of