From Fact to Theory

If continental drift was not rejected for lack of a mechanism, why was it rejected? Some say the time was not ripe. Historical evidence suggests the reverse. The retreat of the thermal contraction theory in the face of radioactive heat generation, the conflict between isostasy and land bridges, and the controversy that Wegener’s theory provoked all show that the time was ripe for a new theory. In 1921, Reginald Daly complained to Walter Lambert about the “bankruptcy in decent theories of mountain-building.” Chester Longwell opined in 1926 that the “displacement hypothesis, in its general form . . . promises a solution of certain troublesome enigmas.” A year later, William Bowie suggested in a letter to Charles Schuchert that it was time for “a long talk on some of the major problems of the earth’s structure and the processes which have caused surface change. The time is ripe for an attack on these larger phases of geology.” One possibility is that the fault lay with Wegener himself, that his deficiencies as a scientist discredited his theory. Wegener was in fact abundantly criticized for his lack of objectivity. In a review of The Origin of Continents, British geologist Philip Lake accused him of being “quite devoid of critical faculty.” No doubt Wegener sometimes expressed himself incautiously. But emphatic language characterized both sides of the drift debate, as well as later discussions of plate tectonics. The strength of the arguments was more an effect than a cause of what was at stake. Some have blamed Wegener’s training, disciplinary affiliations, or nationality for the rejection of his theory, but these arguments lack credibility. Wegener’s contributions to meteorology and geophysics were widely recognized; his death in 1930 prompted a full-page obituary in Nature, which recounted his pioneering contributions to meteorology and mourned his passing as “a great loss to geophysical science.” Being a disciplinary outsider can be an advantage — it probably was for Arthur Holmes when he first embarked on the radiometric time scale. To be sure, there were nation alistic tensions in international science in the early 1920s— German earth scientists complained bitterly over their exclusion from international geodetic and geophysical commissions— but by the late 1920s the theory of continental drift was associated as much with Joly and Holmes as it was with Wegener.