Dr. Young’s Hydraulic Investigations. 165 
his experiments is in all respects extremely satisfactory ; that 
it exhibits a beautiful specimen of the means of expressing the 
general result of an extensive series of observations in an 
analytical formula, and that it does honour to the penetra- 
tion, skill, and address of Mr. Dubuat, and of Mr. de St. 
Honore', who assisted him in the construction of his expres- 
sions. I am by no means disposed to dissent from this enco- 
mium; and I agree with Professor Robison, and with ail 
other late authors on hydraulics, in applauding the unusually 
accurate coincidence between these theorems and the experi- 
ments from which they were deduced. But I have already 
taken the liberty of remarking, in my lecture on the history 
of hydraulics, that the form of these expressions is by no means 
so convenient for practice as it might have been rendered ; 
and they are also liable to still greater objections in particular 
cases, since, when the pipe is either extremely narrow, or 
extremely long, they become completely erroneous: for 
notwithstanding Mr. Dubuat seems to be of opinion, that a 
canal may have a finite inclination, and yet the water con- 
tained in it may remain perfectly at rest, and that no force 
can be sufficient to make water flow in any finite quan- 
tity through a tube less than one twenty-fifth of an inch 
in diameter, it can scarcely require an argument to show that 
he is mistaken in both these respects. It was therefore neces- 
sary for my purpose to substitute, for the formulae of Mr. 
Dubuat, others of a totally different nature ; and I could fol- 
low Dubuat in nothing but in his general mode of considering 
a part of the pressure, or of the height of a given reservoir, 
as employed in overcoming the friction of the pipe through 
which the water flows out of it; a principle, which, if not of his 
original invention, was certainly first reduced by him into a 
