SEISMOLOGICAL DISCOVERY OF VERMILION BAY 7] 
shown in Figure 5 and Figure 6. The solid part of the travel-time 
curves are taken from the negative profile data described in Figure 3. 

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Fic. 4.—Refraction profile layout for partial detail of Vermilion Bay salt dome. 
All four of these profiles show the usual features of a refraction 
profile characteristic of a shallow salt dome. The most essential feature 
is the more or less sudden decrease in apparent velocity shortly after 
387 
