stance—something major and practical that time's stately cycle could do to unravel the earth's history. Volume III is therefore, above all, a long illustration of a new method, striking in its originality and brilliant in its difference from conventional paleontology, for dating rocks of the Cenozoic Era (the last 65 million years, since the extinction of dinosaurs) by percentages of molluscan species still living. I shall show in the next section that this novel method flows directly from Lyell's unusual view of time's cycle applied to life's history.

Although (obviously, from early sections of this chapter) Lyell is not my foremost intellectual hero, I can only describe my reading of the first edition of the Principles as a thrill, a privilege, and an adventure. As I grasped its brilliant coherence about the vision of time's stately cycle, shivers coursed up and down my spine. Yet that thrill has been foreclosed to most readers. The first edition is difficult to obtain, and many reasons conspire to degrade its coherence through the subsequent editions that most geologists read. For one thing, Lyell extracted almost all of volume III, and placed his discussion of the earth's actual history into another book, the Elements of Geology (in later editions, the Manual of Elementary Geology]—thus divorcing his primary application from his verbal defense of time's cycle. For another, Lyell strongly muted his commitment to time's cycle when, late in his career, and with both great personal struggle and splendid honesty (see pages 167–173), he finally admitted the progressive character of life's history. Finally, he shifted and tinkered with so many chapters that the original coherence of argument dissipated, and the last editions almost became, after all, a textbook.

Lyell, Historian of Time's Cycle

Lyell's Explication of History

Hutton and Lyell are indissolubly linked in textbook histories as the two heroes of modern geology—Hutton as unheeded prophet,