ofi Mr. Vince's Observations on the Theory 
thus nearly destroyed, the fluid will be less interrupted at the 
orifice, and consequently will flow out with a greater velocity. 
But why the velocity should also be increased either by in- 
creasing the length of the pipe, or making it an increasing 
cone, under certain limitations, is a circumstance which, I 
confess, I can give no satisfactory reason for. 
The abovementioned experiments were made principally 
with a view to ascertain how far the theory of the motion of 
fluids can be applied ; and the inquiry has led to several cir- 
cumstances which, I believe, have not been observed before. 
That the theory is not applicable in all cases is manifest ; but 
that it brings out conclusions in many instances which agree 
very well with experiment is undoubtedly true. This tends 
to show, either that the common principles of motion cannot 
be applied to fluids, and that the agreement is accidental ; or 
that under certain circumstances and restrictions the applica- 
tion is just. Which of these is the case is not, perhaps, easy 
for the mind to satisfy itself about. Nothing however which 
is here said is done with any view to detract from the merit 
of these celebrated authors. They have manifested uncommon 
penetration, and carried their inquiries upon the subject to an 
extent, that nothing further can be hoped for or expected ; 
and if they had done nothing else in science, this alone would 
have ranked them amongst the very first mathematicians. 
The fault has been non artificis sed artis. 
Mr. Maclaurjn, in his Treatise on Fluxions, has given a 
most admirable illustration of the theory of Sir Isaac Newton. 
It is there a very principal inquiry to determine the ratio of the 
force which generates the velocity of the descending surface 
of the fluid to the force of gravity. Now according to that 
