1the Perpendicular A B at Right angles, which A B muſt hang two
Inches, or thereabouts, from the Wall: Then transferring the
ſtring A B with the Ball into C, let go the ſaid Ball; which you will
82[Figure 82]
ſee firſt to deſcend
deſcribing C B D, and
to paſs ſo far beyond
the Term B, that run
ning along the Arch
B D it will riſe almoſt
as high as the deſigned
Parallel C D, wanting
but a very ſmall mat
ter of reaching to it,
the preciſe arrival thi
ther being denied it by
the Impediment of the Air, and of the Thread. From which we
may truly conclude, that the Impetus acquired in the point B by
the Ball in its deſcent along the Arch C B, was ſo much as ſufficed
to carry it upwards along ſuch another Arch B D unto the ſame
height: having made, and often reiterated this Experiment, let
us drive into the Wall, along which the Perpendicular A B paſſeth,
another Nail, as in E or in F, which is to ſtand out five or ſix In
ches; and this to the end that the thread A B, returning as before
to carry back the Ball C along the Arch C B, when it is come to
B, the Thread ſtopping at the Nail E may be conſtrained to move
along the Circumference B G, deſcribed about the Center E: by
which we ſhall ſee what that ſame Impetus is able to do, which be
fore, being conceived in the ſame term B, carried the ſame Move
able along the Arch B D unto the height of the Horizontal Line
C D. Now, Sirs, you ſhall with delight ſee the Ball carried unto
the Horizontal Line in the Point G; and the ſame will happen if
the ſtop be placed lower, as in F, where the Ball would deſcribe
the Arch B I, evermore terminating its aſcent exactly in the Line
C D: and in caſe the Check were ſo low that the overplus of the
thread beneath it cannot reach to the height of C D, (which would
happen if it were nearer to the point B than to the interſection of
A B with the Horizontal Line C D) then the thread would
whirle and twine about the Nail. This experiment leaveth no
place for our doubting of the truth of the Suppoſition: for the
two Arches C B and D B being equall, and ſcituate alike, the
acquiſt of Moment made along the Deſcent in the Arch C B, is
the ſame with that made along the Deſcent in the Arch D B. But
the Moment acquired in B, along the Arch C B, is able to carry the
ſame Moveable upwards along the Arch B D: Therefore the Mo
ment acquired in the Deſcent D B is equall to that which driveth
Inches, or thereabouts, from the Wall: Then transferring the
ſtring A B with the Ball into C, let go the ſaid Ball; which you will
82[Figure 82]ſee firſt to deſcend
deſcribing C B D, and
to paſs ſo far beyond
the Term B, that run
ning along the Arch
B D it will riſe almoſt
as high as the deſigned
Parallel C D, wanting
but a very ſmall mat
ter of reaching to it,
the preciſe arrival thi
ther being denied it by
the Impediment of the Air, and of the Thread. From which we
may truly conclude, that the Impetus acquired in the point B by
the Ball in its deſcent along the Arch C B, was ſo much as ſufficed
to carry it upwards along ſuch another Arch B D unto the ſame
height: having made, and often reiterated this Experiment, let
us drive into the Wall, along which the Perpendicular A B paſſeth,
another Nail, as in E or in F, which is to ſtand out five or ſix In
ches; and this to the end that the thread A B, returning as before
to carry back the Ball C along the Arch C B, when it is come to
B, the Thread ſtopping at the Nail E may be conſtrained to move
along the Circumference B G, deſcribed about the Center E: by
which we ſhall ſee what that ſame Impetus is able to do, which be
fore, being conceived in the ſame term B, carried the ſame Move
able along the Arch B D unto the height of the Horizontal Line
C D. Now, Sirs, you ſhall with delight ſee the Ball carried unto
the Horizontal Line in the Point G; and the ſame will happen if
the ſtop be placed lower, as in F, where the Ball would deſcribe
the Arch B I, evermore terminating its aſcent exactly in the Line
C D: and in caſe the Check were ſo low that the overplus of the
thread beneath it cannot reach to the height of C D, (which would
happen if it were nearer to the point B than to the interſection of
A B with the Horizontal Line C D) then the thread would
whirle and twine about the Nail. This experiment leaveth no
place for our doubting of the truth of the Suppoſition: for the
two Arches C B and D B being equall, and ſcituate alike, the
acquiſt of Moment made along the Deſcent in the Arch C B, is
the ſame with that made along the Deſcent in the Arch D B. But
the Moment acquired in B, along the Arch C B, is able to carry the
ſame Moveable upwards along the Arch B D: Therefore the Mo
ment acquired in the Deſcent D B is equall to that which driveth