Swiss, Austrian, and French geologist in the preceding 25 years (1875 - 1900) had made sensational discoveries in the Western Alps of massive folds and overthrusts on scales of tens and hundreds of kilometers. These were structure so huge and so physically improbable (how could rocks maintain coherence thrust over such distances?). Most geologists disbelieved the published field reports and had to be convinced as it were on pilgrimage, literally taken to the top of the mountain to undergo conversion. By the turn of the century, the hottest topic in European geology was Alpine tectonics, the folding and thrusting of these huge mountain ranges.