Now that plate tectonics is fast becoming vernacular jargon, the geologists might be said to be having a field day. In contrast to John McPhee's drift-doubter Anita Harris (In Suspect Terrain, below), John Harrington waxes enthusiastic, even poetic, about plate theory. However, geologist Harrington (Southern Methodist University, Emeritus) shares Harris' devotion to field work and data gathering. He also explains the subject at a more elementary level that a general reader might welcome--moving from some rather heavy-handed pedagogy on the nature of science to straightforward chapters mixing history, literary references, and contemporary observations and methods. He literally invites the reader to follow him as he shows, by diagrams and photos, just what the outcrops, unconformities, mid-ocean ridges, and other wonders look like. There are nice background sketches of Herodotus and Eratosthenes, some Chinese scholars and others, up to the 19th-century burst of Agassiz, and the Scots Hutton, Playfair, and Lyell. Intermixed are personal anecdotes--such as the time Harrington split open a rock to discover an ancient but non-fossilized leaf inside that began to crumble before his eyes. What to do? He are it. Only the last chapter deals specifically with plate tectonics. Most of this is accepted wisdom. Harrington clearly differs with Harris, however, in seeing more applications for the theory, especially in the Appalachian chain and eastern shoreline. So there are rumbles in contemporary geology. The curious reader will want to be acquainted with both sides, and the neophyte might well begin with Harrington's deft popularization.