Note 6 — ADDENDA.

Sir James Hall believes that erratic boulders were transported by debacles, when embedded in ice. He seems to have been led to this opinion, by a clear perception of the difficulty of supposing the existence of glaciers in the Alps and in other regions of central Europe, excepting at great altitudes; and from such situations a debacle was absolutely requisite to transport fragments on ice. Sir James rejects the belief of M. Wrede (given on the authority of De Luc), that the boulders of the Baltic may have been brought into their present place by ice, acting, during a steady and slow change in the level of the ocean. M. Wrede, therefore, appears to have been the originator of the theory advocated in this volume; and no country was more likely than Sweden to have given birth to such a theory.