210 
standing that A was a plain cylinder, and B and C were 
coned to a depth of half their thickness and formed tubes 
from three to six diameters in length. Moreover, although 
the results shown in the tables were obtained with the 
coned sides of the orifices inside the vessel ; yet, when the 
sides were reversed, the rate of discharge through A, B, and 
C was only diminished by one-thirtieth part, and there 
was no difference in the rate of discharge through D whether 
the coned side of the orifice was inside or outside the vessel. 
Taking A, B, and C as the orifices producing the maximum 
rate of discharge, we have ’935 as the value of the co-efiicient 
of discharge from an orifice in a thin plate for the highest 
pressure of 1351bs. This value, as will be seen, is the same 
for all the pressures in the table within errors of observation 
and experiment, and the mean value of the coefficient for 
all the pressures is *937. 
Applying this coefficient to the velocity deduced in 
Table I. of my former paper for an orifice in a thin plate, 
we have for the maximum velocity with which air of 
1351bs. pressure rushes into a vacuum, before expansion. 
V = 
750 
•937 
= 800 feet per second. 
Some anomalous rates of efflux from the same orifice 
which were obtained when air of less than 151bs. effective 
pressure was discharged into the atmosphere, induced me to 
make a series of experiments on the discharge of air of an 
initial pressure of 151bs. through the same orifices as in the 
last experiments, and the times were recorded for each 
reduction of 21bs. of pressure. 
All the discharges were made with the conoidal orifices 
inside the vessel, but they were also made through C and D 
with these orifices outside the vessel. The results are 
shown in the following table - 
