io Mr. Vince’s Experiments on the Resistance 
It appears from hence, that the resistance varies as the sine 
of the angle at which the fluid strikes the plane ; the difference 
between the theory and experiment being only such as may be 
supposed to arise from the want of accuracy to which the ex- 
periments must necessarily be subject. 
Let us now first consider, what the whole perpendicular 
resistance by experiment is, when compared with that by 
theory. Now, by theory, the resistance is equal to the weight 
of a column of the fluid, whose base = 0,045 in. and alti- 
tude == 45,1 in. and the weight of that column is = 1 oz. 
1 dwt. 10 grs. Hence, the resistance by theory : the resistance 
■J ■ >5 ’ / $ by experiment : : 1 oz. 1 dwt. 10 grs. : 1 oz. 17 dwts. 12 grs. 
: : 514 : 900. 
In the next place, let us examine what is this resistance, com- 
pared with the resistance of a plane moving in a fluid. We here 
prove, that the resistance of the fluid in motion acting on the 
plane at rest : the resistance by theory : : 900 : 514; and we 
have before proved, that the resistance by theory : the resist- 
ance of a plane body moving in a fluid : : 1598 : 2321 ; hence, 
the resistance of a fluid in motion upon a plane at rest : the re- 
sistance of the same plane, moving with the same velocity, in a 
fluid at rest : : goo x 159 8 : M 4 < * 2 3 21 : : 143 8200 : H9 2 954 
; ; 6:5 nearly. Now we know that the actual effect on the 
plane must be the same in both cases ; and the difference, I 
conceive, can arise only from the action of the fluid behind 
the body, in the latter case, there being no effect of this kind 
in the former case. For, in respect to the pressure before the 
body, that will probably be the same in both cases ; for there 
is a pressure of the column of the spouting fluid, acting against 
