174 DASA 2019-2 ad Figure 23. Scale map of the United Stutes superimposed over crea of major test sites in the Pacific Ocean. From lL. Donaldson. atolls before the Pacific tests were initiated. I recall that the geolo- gists in the group were convinced that the coral was a cap, and in aome of the lectures on the Haven that were held inder Dr, Warren's supervision, we were told that the coral was about 180 feet thick. This was supposed to be so because during the ice age the water had receded to about that level, thus the coral could only grow in th: upper warm layer of water. Therefore, there would be iust a little cap of coral. Many discussions were held as to the possibility of blowing this cap off the top of the mountain on which the coral was superirmposed. These discussions went round and round, Dr. Warren, you recall, during the voyage of the Haven out to the test ground and we listened very intently. In subsequent expeditions to the Marshalls it was possible to drill in the atolls to actually determine the thickness of the coral. During the 1947 expedition particularly, the drilling was geared to go down as much as poszsidly 1,000 feet into the base. Each iuorning when the assembled group would go out to drill we would ask them how they ‘vere coming. "When you're down to 100 feet you ought to be striking base rock the next day."