244 On the Measure of 
cated, and they do not appear to have been 
adopted by succeeding authors. — 
Mr. Waring, of America, has given quite a 
different Diente) which has been approved of 
by several good writers on hydraulics. He 
concludes that the greatest effect will be pro- 
duced when the velocity of the orifice is half 
that of the issuing water; and that this effect 
will be nearly the same as that of a well-con- 
structed undershot water-wheel.* 
The explanation which I have offered of 
the action of the water on this machine is 
different from any other that I have had an 
opportunity of consulting. I offer it, there- 
fore, merely as an attempt to solve an intri- 
~ cate problem. — 
If it were possible for the water to issue 
with the velocity due to the pressure, it is 
“obvious, if my explanation be right, that 
although a very large proportion of the moving 
force of the water may be communicated to 
' the machine, moving with a moderate velocity, 
the maximum of effect can only be obtained 
by an infinite velocity. But when the water 
issues with a velocity which is less than what 
is due to the pressure, as must always be the — 
* American Philos. Trans. yol. 3, p. 191 and 192. 
