calculated and experimental results. The calculated results 
are even more remarkable than the experimental ; for while 
the experiments only show that diminishing the pressure in 
the receiving vessel below a certain limit does not increase 
the flow, the equations show that by such diminution of 
pressure the flow is actually reduced and eventually stopped 
altogether. 
In one important respect however the equations agree 
with the experiments. This is in the limit at which diminu- 
tion of pressure in the receiving vessel ceases to increase the 
flow ; which limit, by the equations, is reached when the 
pressure in the receiving vessel is *527 of the pressure in 
the discharging vessel. 
The equations referred to are based on the laws of thermo- 
dynamics, or the laws of Boyle, Charles, and that of the 
mechanical equivalence of heat. They were investigated by 
Thomson and Joule (see Proc. Koy. Soc , May, 1856), and by 
Prof. Julius Wiesbach (see Civilinginex, 1856); they were 
given by Kankine (articles 137, 137a, Applied Mechanics) 
and have since been adopted in all works on the theory of 
motion of fluids. 
Although discussed by the various writers the theory 
appears to have stood the discussion without having re- 
vealed the cause of its failure ; indeed. Him, in a late work, 
has described the theory as mathematically satisfactory. 
Having passed such an ordeal it was certain that if there 
were a fault it would not be on the surface. But, that by 
diminishing the pressure on the receiving side of the orifice 
the flow should be reduced, and eventually stopped, is a 
conclusion too contrary to common sense to be allowed to 
pass when once it is realized ; even without the direct ex- 
perimental evidence in contradiction, and, in consequence of 
Mr. Wilde’s experiments, the author was led to re-examine 
the theory. 
2, On examining the equations it appears that they con« 
