In opening this discussion on the Origin of the Trias[*][1] I shall restrict myself, as far as possible, to what we can learn about the physical geography and climate of that period from the petrology of the system, leaving one or two points to be more fully described by others. Once for all let me express my obligations for many necessary facts to the Memoirs published by the Geological Survey, especially that on the Triassic and Permian rocks of the Midland Counties, drawn up by Professor Hull in 1869, to suggestive papers on India and Persia by the late Dr. F. Drew and Dr. W. T. Blandford, and to one or two other writers, whom I shall mention in due course. The name Trias, I need hardly say, was given because the rocks of this system in the typical districts of North Central Europe fall naturally into three groups, which in Germany were called, in ascending order, the Bunter, the Muschelkalk, and the Keuper. In our own country the second is missing, and the third is sometimes uncomformable with the first. But, though I think these two represent very distinct chapters in the physical history of Britain, I would not like to assert that no part of the Muschelkalk had a time equivalent in our islands. The Keuper deposits, speaking in general terms, may be followed continuously from the South Devon coast to the Midlands, whence they extend along both sides of the Pennine Range, on the eastern to beyond ... [1]: #fn-1