Perry.] 68 [December 21, 



bed or channel and carry their debris in all the directions pursued by 

 the moving glacier. This does not correspond with the facts 

 observed in drift scratches and drift deposits, for they are invariably 

 from north to south, deviating a little from that general course, the 

 most common direction of drift-scratches being from north-west to 

 south-east in Maine, New Hampshire and Massachusetts, while in 

 Ehode Island they run due north and south. 



Neither the drift scratches nor the drifted materials bear any such 

 relations to the hills and mountains as to indicate a glacial origin or 

 movement. 



American geologists are more inclined to adopt the theory of ice 

 floes, as a drift agency, and the two or more sets of drift scratches, 

 in the ledges, seem to be accounted for by the changing course of 

 tidal currents, moving the grounded ice and gravel on the bottom. 

 It should be remembered that eight-ninths of all floating ice is below 

 the surface of the water, and that ice frequently grounds at the pres- 

 ent time on the Grand Banks, the bottom there being undoubtedly 

 grooved in the same manner as the rocks were in the drift epoch. 

 Dr. Jackson observed that the highest geological authorities rejected 

 the glacial theory of drift, and he need but name De Luc, the veteran 

 geologist of the Alps, Leopold Von Buch of Berlin, L. filie De 

 Beaumont of Paris, the most eminent geologists the world has ever 

 seen, as stern opponents of this theory. 



In response to the invitation of the President, Mr. Perry 

 discussed at some length the objections urged by Dr. Jack- 

 son. 



As to the assertion that the glacier theory is a mere hypothesis, 

 and that the various forms of this theory have been one after 

 another demolished, he would frankly admit that this explanation, 

 in a certain sense, is an hypothesis; it cannot be proved true by a 

 mathematical demonstration ; no more can it be sustained by one 

 kind of evidence alone. But that it is a mere hypothesis, he was not 

 so ready to grant. There is a great variety of considerations bearing 

 on the subject; the argument is cumulative. So, too, if we find, 

 upon examination, that the main effects to be explained are substan- 

 tilaly what we must suppose they would have been in case the coun- 

 try were once covered by an immense blanket of ice ; that there are 

 also facts indicating the prevalence of agencies capable of forming such 



