[ 359 ] 
i. Let the pa- 
rallelogram E re- 
prefent a vefiel 
Jailing in the line 
LR, from left 
hand to right j 
and S, a fixed 
ftation, e. g. a 
caftle,difcharging 
balls in the right 
line S M, per- 
pendicular to the 
route of the vefiel. 
If the vefiel had 
been at reft, a ball 
arriving at the 
middle of it, M, 
would have gone 
right acrofs it, to 
N. But as it is 
fuppofed to be 
failing, the ball 
will not go right 
over from M to 
N, but will crofs 
the deck obliquely, in another right line, as M O, 
and fo will be left behind towards the Bern as much 
as the vefiel had gone forward, while the ball was 
eroding it ; and MN will be to NO as the velocity 
of the ball to the velocity of the vefieh Thus, to 
the people on board, the ball would feem to move 
obliquely acrofs the deck, as if it came from fome 
point 
