TEST B: UNDERWATER EXPLOSION 



almost perfect agreement with predictions made before 

 the tests. These predictions were based on small scale 

 experiments made by the Oceanographic Group at the 

 United States Naval Electronics Laboratory, San 

 Diego, California, and the Naval Mine Warfare Test 

 Station at Solomons Island, Maryland. The explosive 

 charges used in those experiments contained TNT and 

 weighed from one to 2000 pounds. 



The first wave, the highest of all, contained several 

 million tons of water. It traveled with a speed of the 

 order of fifty miles per hour, which is just what the 

 wave experts had predicted.* 



At the start of its outward travel, the first wave was 

 in unstable condition ; its crest tended to get ahead of 

 its base. The result was what oceanographers call a 

 spilling breaker. But as the wave moved along, its 

 height diminished and it lost its tendency to break. 



The first wave soon found itself less high than the 

 second wave ; and a little later the third wave claimed 

 pre-eminence. This handing down of the honors from 

 one wave to the next was in full accord with the expecta- 

 tions of the oceanographers, who say that the gf^otip 

 velocity is less than the phase velocity. 



* The prediction made hy Commander Roger Revelle and Dean 

 M. P. O'Brien was based on the known depth of the lagoon and 

 on the rough rule that in shallow water of specified depth all very 

 long waves have the same velocity. Knowing the depth, they could 

 compute the velocity. In really deep water, of course, the situation 

 is entirely different: a wave's velocity depends on its length, long 

 waves traveling faster than short ones. 



161 



