Lyell's oversights were not inconsiderable. He failed to explain convincingly how mountain ranges were formed and overlooked glaciers as an agent of change. He refused to accept Louis Agassiz's idea of ice ages—"the refrigeration of the globe," as he dismissively termed it—and was confident that mammals "would be found in the oldest fossiliferous beds." He rejected the notion that animals and plants suffered sudden annihilations, and believed that all the principal animal groups—mammals, reptiles, fish, and so on—had coexisted since the dawn of time. On all of these he would ultimately be proved wrong.

Yet it would be nearly impossible to overstate Lyell's influence. The Principles of Geology went through twelve editions in Lyell's lifetime and contained notions that shaped geological thinking far into the twentieth century. Darwin took a first edition with him on the Beagle voyage and wrote afterward that "the great merit of the Principles was that it altered the whole tone of one's mind, and therefore that, when seeing a thing never seen by Lyell, one yet saw it partially through his eyes." In short, he thought him nearly a god, as did many of his generation. It is a testament to the strength of Lyell's sway that in the 1980s when geologists had to abandon just a part of it to accommodate the impact theory of extinctions, it nearly killed them. But that is another chapter.