Association of American Geologists and Naturalists. 139 



produced these effects, was held m its place by a mighty agency, 

 and that it would hare turned to the right or left when it encounter- 

 ed the resistance of the mountains, if it had been possible for it to 

 have done so. Stria) are not only marked upon the rocks in situ, but 

 deep valleys are cut in their surfaces. And it is only upon the 

 struck side that these marks are to be observed. He had arrived at 

 the conclusion that, whether in the form of an iceberg or a glacier, 

 it was ice in mass which had produced the effects above referred to. 

 He could not believe that waves of translation were, of themselves, 

 sufficient to accomplish these results. 



Proi'essor Silliman asked Captain Wilkes if it was within his own 

 knowledge whether the iceberg in the Southern Ocean, along which 

 the vessels of the Exploring Expedition coasted for some 60 or 70 

 miles, was attached to the coast or was afloat. He replied that it 

 was not afloat. Mr Redfield could generally coincide in the views 

 expressed by Professor Hitchcock. He felt inclined to admit that 

 icebergs were the principal agency in causing the striae, rounded, and 

 polished surfaces of the i-ocks of this country and Europe. He did 

 not believe that there was any such antagonism in the glacier and 

 iceberg theories. It was difficult to explain, on the iceberg theory, 

 how the different strire have been produced ; but he believed it more 

 difficult to explain the same phenomenon on the theory of the gla- 

 ciers. Waves of translation have been unfrequent. 



M. Desor remarked that scratches were observed on the mountains 

 of Scandinavia at a height of 6000 feet, on the W^hite Mountains, 

 New Hampshire, at a height of 5000 feet. Mount Washington, which 

 is some 5300 feet high, is not scratched ; its top is covered with 

 loose boulders, presenting a fine specimen of what has been denomi- 

 nated a lake of stones. Just beneath the summit of this mountain 

 the scratches take the general direction of the scratches in the 

 harbour of Boston. The scratches are observed at heights of 5000 

 feet, 10 feet, and below the surface of the water, but to what depth 

 is not at tlie present time known. The same is true of the 

 mountains of Scandinavia. The glaciers of Greenland do not run 

 beneath the sea, but form a vertical walk at its surface, where the 

 water melts the ice, and large icebergs are broken off and float away. 

 Murchison says that glaciers have left their marks as far as the 

 mountains extend, but that currents have produced the phenomena 

 observed in the valleys. This cannot be true, for the strije of the 

 mountains and valleys preserve one general direction. Now the 

 strire being similar in character when observed in different parts 

 of the world, ho was led to conclude that one general course had 

 produced these effects. 



Mr Redfield did not think that the stria) were marked upon the 

 mountains and valleys at the same time. 



llemarks were also made by Dr Reed, and Prof. H. D. Rogers. 



