Textbooks teach the principles of science. Lyellʼs geology textbooks emphasized vertical crustal movement. He avoided far-fetched continental-drift hypotheses by Hopkins in 1844 and Pepper in 1861. Their notions of drift were supported by fossil and paleoclimate evidence, but their causes were global magnetism and electrochemical crystallization and dissolution. 
 
Danaʼs textbooks from 1863 to 1895 taught that the symmetry of North America proved it had always stood alone; thus Americans were conditioned to reject Wegenerʼs concept of a Carboniferous supercontinent. 
Unaware of Wegenerʼs hypothesis in 1912, Schuchert launched a textbook series that guided American geological opinion from 1915 to the 1960s. His paleogeographic models required Carboniferous land bridges to connect fixed continents. He and coauthors Longwell and Dunbar eventually realized that Wegenerʼs continental-drift hypothesis would disprove land-bridge theory and solve problems of mountain ranges, paleoclimates, and fossil distributions, but they guarded against it in their textbooks. 
 
Already in 1927, Holmes proposed that convection with sea-floor spreading drove continental drift, but editor Schuchert would not publish that breakthrough. 
 
Geologists Du Toit, Van der Gracht, Holmes, Shand, Bailey, and Grabau showed the merits of continental drift, but their publications had little impact. 
 
Willis accepted the invitations of Schuchert in 1932 and Longwell in 1944 to write papers opposing Wegenerʼs hypothesis. Simpson contributed with paleontologic opposition.
 
 In 1944 Holmes published a British textbook that showed how continental drift could change geology. It was Holmes, Carey, and Wilson, as much as the Americans Hess and Dietz, who should be credited with instigating the plate-tectonic revolution.

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