3 oo POPULAR SCIENCE MONTHLY 



THE DEVELOPMENT OF THE GLACIAL HYPOTHESIS 



IN AMERICA 1 



By Dr. GEORGE P. MERRILL, 



U. S. NATIONAL MUSEUM 



GEOLOGY is preeminently a science of observation and deduction. 

 Certain phases of it are, nevertheless, dependent upon advances 

 in other branches. As the science grows this mutual interdependence 

 becomes more and more apparent, and it is perhaps now questionable 

 if further advance, aside from a purely geographic extension of knowl- 

 edge relative to the distribution of geologic groups, is possible without 

 calling in the aid of physics and chemistry. 



Among those phases of geology which have been most independent 

 of the. allied sciences, and in which the gradual development of the 

 power to observe correctly and deduce accordingly can incidentally be 

 readily studied, the phenomena of the drift stand prominent. They 

 furnish, moreover, an excellent example of the growth of knowledge 

 through cumulative evidence, since of all phenomena, those relating to 

 the drift have, in America, been perhaps longest under observation. 

 In that which follows, however, it has been my principal aim to trace 

 the gradual progress of the glacial hypothesis in America. Beyond 

 this my references are purely incidental. 



Out of numerous observations relating to the phenomena of the 

 drift and, incidentally, to glaciation, those which seem most worthy 

 of consideration at the present time were by Benjamin De Witt and 

 are to be found recorded in the second volume of the ' Transactions ' 

 of the Philadelphia Academy for 1793. 



De Witt noted the occurrence, along the shores of Lake Superior, 



of boulders representing a large variety of rocks, sixty-four different 



types being collected. In the discussion of this occurrence, he remarks : 



Now, it is almost impossible to believe that so great a variety of stones 

 should be naturally formed in one place. . . . They must, therefore, have 

 been conveyed there by some extraordinary means. I am inclined to believe 

 that this may have been effected by some mighty convulsion of nature, such 

 as an earthquake or eruption, and perhaps this vast lake may be considered 

 as one of those great ' fountains of the deep ' which were broken up when the 

 earth was deluged with water, thereby producing that confusion and disorder 

 in the composition of its surface which evidently seems to exist. 



This, so far as I am aware, is the first attempt to account for the 



1 Adapted from a presidential address delivered December 13, 190.3, before 

 the Geological Society of Washington. 



