"The old diluvialists were induced by their system to confound all the groups of strata together instead of discriminating,—to refer all appearances to one cause and to one brief period, not to a variety of causes acting throughout a long succession of epochs. ...Under the influence of such prejudices, three centuries were of as little avail, as a few years in our own times, when we are no longer required to propel the vessel against the force of an adverse current."