which is the velocity of sound in the gas at the absolute 
temperature 
It thus appears that the velocity of gas at the point of 
minimum area of a stream along which the pressure falls 
continuous is equal to the velocity of sound in the gas at 
that point. 
8. From the equation of flow (5) it appears that for every 
value of A other than its minimum value, there are two 
possible values of the pressure which satisfy the equation, 
one being larger and the other less than 
• 527^1 
It therefore appears that in a channel having two equal 
minima values of section A and C as iii fig. 6 
the flow from A to B may take place in either of two ways 
when the velocity is such that the pressure at A and C is 
•527 _pi i.e. the pressure may either be a maximum or a 
at B. In this respect gas differs entirely from a liquid with 
which the pressure can only be a maximum at B. 
9. For air through an orifice since 7= 1*408. When the 
pressure in the receiving vessel is less than *527j9i, the nume- 
rical value of the velocity in the neck of the orifice is 
U^ = 997 (feet per sec.) - (13) 
and if the temperature is 57° Fahr. as in Mr. Wilde’s experi- 
ments, 
U,= 1022 (14) 
reducing this in the ratio of the density at the neck to the 
density in the discharging vessel 
