The difficulty is the same as that felt by so many geologists, when Lyell first insisted that long lines of inland cliffs had been formed, and great valleys excavated, by the agencies which we still see at work.
Zailtasun hau hainbat geologok nabaritu zutena bera da, Lyellek lehen aldiz defendatu zuenean egun ere lanean ikusten ditugun eragileak izan direla barnealdeko labar lerro luzeak eratu eta haran zabalak indusi dituztenak.