Page:The Journal of geology (IA journalofgeology11893univers).pdf/435

erland. This map, which was published on a scale of 1:100,000 in 1885, embraces the area between the St. Gotthard railway and the Rhein, north of the great central (Tessin) massif which forms the south flank of the Alps. Hence it includes the eastern portion of the Aar and Gotthard massifs, with all the younger formations in their most disturbed and implicated development. The thirteen years which have elapsed since the appearance of the earlier work have so greatly multiplied observations and stimulated thought that the standpoint regarding the whole subject of dynamic metamorphism is seen to be far advanced. Nor has Professor Heim himself been instrumental in any small way in bringing about this result. Aside from his own detailed field work, his suggestions as to the efficacy of orographic movement as a metamorphosing agent have been of profound and world-wide influence. Hence we cannot be surprised that he should have inspired enthusiastic students within the limits of his own special field. Others have worked out under his direction many details upon which some of his own broadest and most far-reaching generalizations rest. Some of the best of these results appear almost simultaneously with his latest work and form an integral portion of it. This is notably true of the special petrographic studies of both the eruptive and sedimentary rocks of two important and much discussed horizons—the Bündnerschiefer and the Verrucano—in both of which the processes of dynamometamorphism can be made out clearly and precisely followed.

More than one quarter of the Swiss atlas sheet XIV is occupied by that diversified complex of phyllites and schists, called by Heim the Bündnerschiefer. Their stratigraphical relations are, on account of the dislocations to which they have been subjected, often very obscure. They have been variously interpreted by different observers, but as the result of years of mature observation Professor Heim gives a full presentation of the facts, and now concludes that he must differ with Bonney, Gümbel, Diener and others who have ascribed to them a greater age, and agree with A. Escher v. d. Linth, Theobold and Rolle who regard them as a united and continuous series belonging in the main to the Lias. Toward the east, where these schists have their broadest and least disturbed development, they are comparatively little altered, and consist of calcareous shales and phyllites, impure limestones, sandstones, dolomitic and gypseous beds, interstratified with green schists and serpentine which are shown by microscopical exam-