10 Nits ZEILON, 
we have, for instance, y determined from: 
Wrage. Ve 
3 
I 9 : 
oq = jou coth kA" — ky ZEN do) dee 
From this formula and the corresponding one for w, these functions 
are computed by successive approximation. The first approximation will 
give for g and w expressions containing factors of the order of magni- 
tude: 
y 
f? dz 
0 
It is natural to regard this integral, which in a way measures the ex- 
tension of the transition layer, as a small quantity whose higher 
powers may be neglected. Proceeding to the higher approximations 
we conclude that in integrals of the form: 
kf ow dz. and [Op dz 
the principal term would be of the order 
Prazfe du , 
0 0 
> 2 
which, by the theorems of mean values, is of the order of (Jo) » 
0 
and hence negligible. On the other hand: 
54 d 
| Ó 22 dz 
J dz 
y 
would be of the order f 024 , a quantity which may have to be re- 
0 
tained. Consequently in the first approximation we take: 
