When a subject as dry and obscure as geophysics is rendered absolutely engrossing, one has to take note. Wertenbaker writes of the man who revolutionized earth science in his seismic mappings and soundings of the ocean, his samplings of the core, and his collection of earthquake data. It seems that Ewing simply approached the earth as a physicist, rather than a geologist, and asked such questions as, "". . . Why are the ranges long and narrow, instead, perhaps, of being round?. . . Why are there mountains at all? Why are there earthquakes? What is tearing the earth apart, and why in California when not in Connecticut?"" His consuming drive and maverick techniques eventually led to the recognition of the Mid-Ocean Ridge, predictions of the earth's magnetic reversal, and the tectonic plate model of continental drift. It may sound recondite, but it becomes intelligible when Wertenbaker writes about it. Part of the author's skill lies in his portrayal of the human dramas (Ewing and fellow workers being swept overboard in high seas) and the politics of research. But most of it lies in simply writing well -- conveying a knowledge of and enthusiasm for his material.