function. For larger values of m and j, the time required in- 
creases very rapidly, and the use of electronic computers might 
be advisable. 
The reliability of the results 
ie [ay(# ,0)]° were determined by the procedures described 
above, there would be some doubt as to the reliability of the re- 
sults, especially for small values of m and qe They would at least 
give an indication of the values of the function but the degree of 
confidence in the final numerical results in terms of the number 
of degrees of freedom cannot be given at this time. 
The airborne altimeter might introduce additional error by 
reflecting in part the effect of atmospheric turbulence as sug= 
gested by Tukey in a recent conference. A stereoptican measure- 
ment of 17 (x') for different e* from a photograph would eliminate 
errors due to the effect of turbulence. 
Ge [a,(#,0)]° is a function which has been filtered by the 
travel of the disturbance from the source so that it is confined 
to a small area of the H ,© plane, just a few directions of & would 
yield, along with the observation of 7(t), a great deal of inform- 
ation about Ean cu seule 
Other methods for the determination of [a ( #0) 1° 
es cS SS ST 
In a recent conference, Tukey suggested another method for 
the determination of [a5 (m ,e)]° by the use of the stereoptican 
measurements. The method depends on many parallel measurements 
for different y' in the x' direction. Waves not traveling in 
the x! direction can be partly filtered out by the addition of 
values on a line y' equals constant. The details of the procedure 
= 309 - 
