A Very Trusting Man - Four Revolutions in the Earth Sciences - page 61

Instead of following up in the next chapter with detailed geological evidence,
Wegener turned to his weakest argument, which he had proposed in one of his pa-
pers from 1912: the use of astronomical positioning to show that the continents are
drifting today. But as the method had led nowhere, the chapter in the 1929 edition
petered out: “The complete interpretation of these matters will only be possible
after a more prolonged series of observations has been made, and whether a clear
understanding of the older shifts will ever be reached seems doubtful in the cir-
cumstances” (34). Why then include it, at least so prominently, something that no
lawyer would have done? Perhaps because Wegener was indeed “a very trusting
man.”
The discussion of isostasy and the nature of the Earth's interior led Wegener to
two particularly important observations. First, “if . . . the continental blocks really
do float on a fluid . . . there is clearly no reason why their movements should only
occurverticallyandnotalsohorizontally”(45).Second,“underforcesappliedover
geological time scales, the earth must behave as a fluid [as] shown by the fact that
its oblateness corresponds exactly to its period of rotation” (56).
Thesetwostatements arereasonenoughforscientists tohaveincluded horizont-
al movements, that is, continental drift, among their working hypotheses, if indeed
there were any other hypotheses, permanence, contraction, and land bridges each
having been refuted.
NowWegener turned tothe geological evidence, which “provide[s] averyclear-
cut test of our theory.” Had the continents once been connected, “many folds and
other formations that arose before the split occurred would conform on both sides”
(61). Were we to rejoin today's continents, “it is just as if we were to refit the torn
pieces of a newspaper by matching their edges and then check whether the lines of
print run smoothly across,” he wrote. “If they do, there is nothing left but to con-
clude that the pieces were in fact joined in this way” (76).
By this time, Wegener had the advantage of being able to read the lines of news-
print with a superb magnifying glass. In 1927, the South African Alexander Du
Toit had made an extensive field comparison of South American and African geo-
logy. 10 Du Toit found so many similarities that to summarize them took seven
pages. His most striking conclusion was that “particular formations along the two
opposed shores [of South America and southern Africa] tend to resemble each oth-
er more closely” than either resembles the geology immediately within its own
continent. 11
WegenernextcomparedthegeologyoftheNorthAtlanticcontinents.Theyhave
similar mountain ranges: the Appalachians and in northern Britain and Norway,
the Caledonides. For Gondwanaland the putative southern supercontinent, Wegen-