86 Lecture 4 
of that medium. If the disturbances of the base followed a simple pattern, i.e., 
a piston motion, the medium could be represented by a very simple pendent net - 
work. In ships, the base was liable to be stimulated into a very complicated 
pattern which might be significantly influenced by the existence of the outside 
medium. Dr. Flint did not see clearly, however, that to resort to electrical 
analogs was going to give any clearer qualitative understanding of the problems 
involved in reducing energy transmission into the medium or any greater facility 
in quantitative analysis of particular situations. 
PROFESSOR R. E.H. RASMUSSEN complimented the lecturer on his clear 
exposition and wondered whether he had studied the effect of mechanical dis- 
turbances, due to traffic, on the stability of laboratory instruments. He also 
asked Dr. Parfitt for practical results obtained by using mechanical isolating 
mounts. 
DR. PARFITT: Unfortunately, I have no figures on vibration caused by traffic. 
Actual field results on the benefit obtained from isolation systems are very 
difficult to come by since comparable before-and-after measurements are 
hardly ever possible. I have no reason, however, to think that the simple theory 
is not applicable, except insofar as the foundation impedance is not usually 
well known. 
