The latest in Sullivan's How Do They. . . series takes its unity not from the problems he covers but from the methods used to solve them. Thus the chapters range from such trivial matters as coin scrounging and electronic baggage inspection (for spotting skyjackers) to finding oil, natural gas, iron and copper; Sullivan's umbrella title also allows him to go on about how water is found with dowsing rods, enemy subs with sonar, and tornadoes with radar. All of this has some appeal for the idly curious, but Sullivan hits his stride in the more substantial chapters on geophysical exploration, where his empathy with the nontechnical mind shows up in his comparison of the seismic survey to ""a pen and ink drawing of a wedge of layer cake."" More basically, ""There are no lakes; there are no pools (of oil). It is found within porous rocks."" And, as a curiosity, we're told not only that the Geiger counter is being replaced as a radioactive mineral detector by a scintillation counter that responds to gamma rays, but also that in parts of Canada the presence of abnormal blueberries is the telling indicator of uranium deposits. Despite some pseudo-dramatic chapter openers (""For an eleven-year-old girl, Carol Terbush was acting in a very strange manner. . .""), a browser's find.