time, continental drift was not accepted. Some of these ideas were discussed in the context of abandoned fixist ideas of a deforming globe without continental drift or an expanding Earth. They were published during an episode of extreme political and economic instability that hampered scientific communication. Many were published by European scientists and at first not mentioned or given little credit in the papers on sea floor spreading published by the American researchers in the 1960s. Mid-oceanic ridge spreading and convection In 1947, a team of scientists led by Maurice Ewing utilizing the Woods Hole Oceanographic Institution's research vessel Atlantis and an array of instruments, confirmed the existence of a rise in the central Atlantic Ocean, and found that the floor of the seabed beneath the layer of sediments consisted of basalt, not the granite which is the main constituent of continents. They also found that the oceanic crust was much thinner than continental crust. All these new findings raised important and intriguing questions. The new data that had been collected on the ocean basins also showed particular characteristics regarding the bathymetry. One of the major outcomes of these datasets was that all along the globe, a system of mid-oceanic ridges was detected. An important conclusion was that along this system, new ocean floor was being created, which led to the concept of the "Great Global Rift". This was described in the crucial paper of Bruce Heezen (1960) based on his work with Marie Tharp, which would trigger a real revolution in thinking. A profound consequence of seafloor spreading is that new crust was, and still is, being continually created along the oceanic ridges. For this reason, Heezen initially advocated the so-called "expanding Earth" hypothesis of S. Warren Carey (see above). Therefore, the question remained as to how new crust could continuously be added along the oceanic ridges without increasing the size of Earth. In reality, this question had been solved already by numerous scientists during the 1940s and the 1950s, like Arthur Holmes, Vening-Meinesz, Coates and many others: The crust in excess disappeared along what were called the oceanic trenches, where so-called "subduction" occurred. Therefore, when various scientists during the early 1960s started to reason on the data at their disposal regarding the ocean floor, the pieces of the theory quickly fell into place. The question particularly intrigued Harry Hammond Hess, a Princeton University geologist and a Naval Reserve