1would not ſuffer it to gain coming from never ſo great an height:
for in caſe the Velocity impreſſed upon it by the Fire ſhould not
exceed that which it might acquire of its ſelf deſcending naturally,
the battery downwards ought rather to be more valid than leſs.
I have not made ſuch an Experiment, but incline to think that a
Musket or Cannon Bullet falling from never ſo great an height,
will not make that percuſſion which it maketh in a Wall at a Di
ſtance of a few yards, that is of ſo few that the ſhort perforation,
or, if you will, Sciſſure to be made in the Air ſufficeth not to ob
viate the exceſs of the ſupernatural impetuoſity impreſſed on it by
the Fire. This exceſſive Impetus of ſuch like forced ſhots may
cauſe ſome deformity in the Line of the Projection; making
the beginning of the Parabola leſs inclined or curved than the end.
But this can be but of little or no prejudice to our Author in
practical Operations: amongſt the which the principal is the com
poſition of a Table for the Ranges, or Flights, which containeth
the diſtances of the Falls of Balls ſhot according to all Elevations.
And becauſe theſe kinds of Projections are made with Mortar
Pieces, and with no great charge; in theſe the Impetus not being
ſupernatural, the Ranges deſcribe their Lines very exactly.
for in caſe the Velocity impreſſed upon it by the Fire ſhould not
exceed that which it might acquire of its ſelf deſcending naturally,
the battery downwards ought rather to be more valid than leſs.
I have not made ſuch an Experiment, but incline to think that a
Musket or Cannon Bullet falling from never ſo great an height,
will not make that percuſſion which it maketh in a Wall at a Di
ſtance of a few yards, that is of ſo few that the ſhort perforation,
or, if you will, Sciſſure to be made in the Air ſufficeth not to ob
viate the exceſs of the ſupernatural impetuoſity impreſſed on it by
the Fire. This exceſſive Impetus of ſuch like forced ſhots may
cauſe ſome deformity in the Line of the Projection; making
the beginning of the Parabola leſs inclined or curved than the end.
But this can be but of little or no prejudice to our Author in
practical Operations: amongſt the which the principal is the com
poſition of a Table for the Ranges, or Flights, which containeth
the diſtances of the Falls of Balls ſhot according to all Elevations.
And becauſe theſe kinds of Projections are made with Mortar
Pieces, and with no great charge; in theſe the Impetus not being
ſupernatural, the Ranges deſcribe their Lines very exactly.
* Or Way.
* Or battered.
But for the preſent let us proceed forwards in the Treatiſe,
where the Author deſireth to lead us to the Contemplation and
Inveſtigation of the Impetus of the Moveable whilſt it moveth
with a Motion compounded of two. And firſt of that compoun
ded of two Equable Motions; the one Horizontal, and the other
Perpendicular.
where the Author deſireth to lead us to the Contemplation and
Inveſtigation of the Impetus of the Moveable whilſt it moveth
with a Motion compounded of two. And firſt of that compoun
ded of two Equable Motions; the one Horizontal, and the other
Perpendicular.
THEOR. II. PROP. II.
If any Moveable be moved with a twofold Equa
ble Motion, that is, Horizontal and Perpen
dicular, the Impetus or Moment of the Lation
compounded of both the Motions ſhall be po
tentia equal to both the Moments of the firſt
Motions.
ble Motion, that is, Horizontal and Perpen
dicular, the Impetus or Moment of the Lation
compounded of both the Motions ſhall be po
tentia equal to both the Moments of the firſt
Motions.
For let any Moveable be moved Equably with a double Lation,
and let the Mutations of the Perpendicular anſwer to the Space
A B, and let B C anſwer to the Horizontal Lation paſſed in
the ſame Time. Foraſmuch therefore as the Spa-
147[Figure 147]
ces A B, and B C are paſſed by the Equable Mo
tion in the ſame Time, their Moments ſhall be to
cach other as the ſaid A B and B C. But the
Moveable which is moved according to theſe two Mutations ſhall de-
and let the Mutations of the Perpendicular anſwer to the Space
A B, and let B C anſwer to the Horizontal Lation paſſed in
the ſame Time. Foraſmuch therefore as the Spa-
147[Figure 147]ces A B, and B C are paſſed by the Equable Mo
tion in the ſame Time, their Moments ſhall be to
cach other as the ſaid A B and B C. But the
Moveable which is moved according to theſe two Mutations ſhall de-