25 
lower pressures would be much different. This is specially 
noticeable for the velocity (842 feet per second) assigned to 
atmospheric pressure of 15 lbs., and as it was a matter of 
much interest that this important constant of nature should 
be determined with all the accuracy attainable, experiments 
were made to ascertain the velocity of discharge for every 
lb. of pressure from 15 lbs. to 21bs. In these experiments 
the readings were taken from the mercurial gauge and the 
vacuum in the chamber was reduced to 0*4 of an inch of 
mercury. 
The results obtained are shown in the table. 
Table IT, 
Discharge into a Vacuum 0’4in. Mercury. 
Barometer 29 -96. . Thermometer 60° F. 
Absolute 
pressure in lbs. 
per 
square inch. 
Time of 
discharge 
in 
seconds. 
Velocity 
in feet 
per second. 
Velocity 
coefficient 
•62 
15 
16-0 
i 
633 
1021 
14 
17-5 
1 621 
1001 
13 
19-0 
1 614 
990 
12 
21-0 
1 606 
977 
11 
23-0 
600 
968 
10 
25-5 
596 
961 
9 
28-5 
593 
956 
8 
32-5 
584 
942 
7 
37-5 
577 
931 
6 
45-0 
563 
908 
5 
55-0 
559 
901 
4 
70-0 
542 
874 
3 
102-0 
497 
802 
2 
180-0 
421 
679 
By a calculation similar to that for the higher pressures, 
we obtain for the initial velocity with which the atmosphere 
rushes into a vacuum through a hole in a thin plate 
573 265-25 
633 per second. 
Or V = ^ = 1021 
•62 
feet per second for the contracted vein. 
That the difference between the theoretic and experi- 
mental velocities was not caused by the friction of the 
stream of air against the circumference of a smaller orifice 
