Peterson 
said avout the possibility of the bubbles being of almost neutral densi- 
ty, perhaps it is then very likely that such nuclei follow the stream- 
lines or very close to them. It is our belief from work that we have 
done more recently at our laboratory that bubbles following these 
streamlines merely have to enter the low-pressure field of the head- 
form in order to produce cavitation (1). Of course, more bubbles will 
cavitate near the body than farther from it. 
DISCUSSION 
Serge Bindel 
Délégatton Générale ad la Recherche Setenttfique et Techntque 
Parts, France 
( Translated from French) 
I read with a great interest the paper presented by 
Dr. Peterson and I must say firstly that I do not agree completely 
with its last conclusion, When Dr. Peterson tells us that his paper is 
a contribution among others about cavitation and that there is nothing 
original in its conclusion, I frankly believe that he is too modest. In 
fact this contribution seems to be very important in several respects. 
First due to the nature itself of program, and to the quality of the 
measurements. In particular, it seems to me that for the first time 
the bubble spectrum in front of the test body has been measured, not 
only the spectrum of free bubbles but also that of the solid particles 
by means of an unquestionable method, here the holographic one. That 
leads to estimate that the author's conclusions are based on serious 
data and consequently that this paper is by no means negligible. 
This point being reminded, I would like to make for my part 
two series of remarks ; first on the analytical calculation of the tra- 
jectories. It has to be pointed out what are the limits of such a cal- 
culation ; it is based on some simplifying hypotheses, which are not 
original, but these hypotheses are not completely valid, even far from 
the body. As was shown for example by Foissey in a recent paper 
(1) SCHIEBE, F.R., ''Measurement of the Cavitation Susceptibility 
of Water Using Standard Bodies", Proj. Rpt. No. 118, 
St. Anthony Falls Hydraulic Laboratory, 1971. 
1182 
