66 
Substituting from equations (1) 
J P 
7 Po-^ 
r - 1 po 7*0 
' ^97 Po ’■« / 
l_f, 
p '\r "1 
y - 1 Po pi t 
nj 7 , 
'-'-m & - ; ■■■<*' 
■' i- 
Hence along a steady stream since W is constant equa- 
tion (5) gives a relation that must hold between A and p. 
dA 
Differentiating A with respect to p and making ^ zero, 
it appears 
y-l 7"1 
2^1 7 =(y+l)i3 7 
or 
-(v-f.) 
7 
y-1 
,( 6 ) 
.(7) 
For air y = 1*408, 
^=■527 ( 8 ) 
Pi 
It thus appears that as long as p falls, the section con- 
tinuously diminishes to a minimum value when p = '527pi, 
and then increases again. Substituting this value of p in 
equation (3) 
„ = V {^rmr - } 
(r + )poTo 
. y-1 
v/2ys'?>„ /p \ 2y 
(9) 
(10) 
(r + l)po+ \i?o/ 
V^ygPofPo'^^fPi\\^ 
{7+^)Po\pJ \p/ 
(11) 
Hence by equation (6) 
A/ yg 
^ 7oTo 
(12) 
