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.4 Mr, Vince’s Experiments on the Resistance 
whole of that part of the force which, after resolution, acts 
parallel to the plane; whereas (from the experiments which 
will be afterwards mentioned), it appears that part of that 
force acts upon the plane ; also, the resistance of the fluid 
which escapes from the plane, into the surrounding fluid, may 
probably tend to increase the actual resistance above that which 
the theory gives, in which that consideration does not enter; but, 
as this latter circumstance affects the resistance at all angles, 
and we do not know the quantity of effect which it produces, 
we cannot say how it may affect the ratio of the resistances at 
different angles. 
In theory, the resistance perpendicular to the planes is sup- 
posed to be equal to the weight of a column of fluid, whose 
base = 3,73 in. and altitude = the space through which a body 
must fall to acquire the velocity of o ,66 feet ; now that space 
is 0,08124 in. consequently the weight of the column = 0,1598 
Troy oz. ; but the actual resistance was found to be = 0,2321 oz. 
Hence, the actual resistance of the planes : the resistance in our 
theory :: 0,2321 : 0,1598, which is nearly as 3 : 2. 
I am aware that experiments have been made upon the re- 
sistances of bodies moving in water, which have agreed with 
our theory. An extensive set was instituted by D’Alembert, 
Condorcet, and Bossut, the result of which very nearly 
coincided with theory, so far as regards the absolute quantity 
of the perpendicular resistance. Their experiments were made 
upon floating bodies, drawn upon the fluid by a force acting 
upon them in a direction parallel to the surface of the fluid. 
There can be no doubt but that these experiments were very 
accurately made. The experiments here related were also re- 
peated so often, and with so much care, and the results always 
