More than once your speaker has had occasion to say that Iowa was exceptionally fortunate in its location with reference to the movements and marginal limits of the successive ice invasions of the Glacial epoch, and that the state therefore offers unusual facilities for the study of the relative age and differential characters of the several sheets of drift. It is not to be understood from this, however, that in the favored area selected for discussion there are no unsettled Pleistocene problems. Important questions, many of them, are still waiting for solution; but while knowledge is admittedly incomplete in many particulars, it may be worth the while at this stage in the interpretation of Pleistocene records to set out the points that seem to be indicated with a fair degree of clearness. In the discussion which is to follow no attempt will be made to give an historical outline of the . . .