612 



SCIENCE 



[N. S. Vol. XXXVII. No. 955 



surely the lower block could not have been 

 moved, and the upper block would not have 

 moved contrary to the ice motion. If the slip- 

 ping can be explained by frost action, the 

 positions of the other blocks can not, for they 

 have evidently been thrown about by some 

 -other force. Furthermore if moving ice 

 caused the confusion, one would naturally ex- 

 pect to find several different kinds of rock in 

 the gorge. As far as I have explored the river 

 one kind of rock only is present, a rather 

 coarse biotite granite. A dark schist occurs 

 in Beaver Meadows and some fragments of 

 this should be found in Lost River only half 

 a mile away. In the true moraines 100 yards 

 away to the south, abundant fragments of this 

 schist are found, but nothing of the kind in 

 Lost Eiver. 



The fact that many of the potholes are 

 cracked, disrupted and weathered as deeply 

 as rocks outside of the gorge makes it evident 

 that most of the potholes were formed before 

 the main force which caused the confusion 

 eam.e. In any event most of the potholes were 

 formed when the river had much more sedi- 

 ment than at present, and presumably this was 

 during Glacial Period times, or at least when 

 the ice had not retreated wholly from Kins- 

 man Notch. The present amount of flow of 

 very clear water is too small to account for 

 the larger potholes. The largest of all is about 

 twenty-five feet in diameter, narrowing toward 

 the top. It has been badly broken and about 

 one half only remains in position. 



From the extraordinary positions of some of 

 the water-worn channels it seems possible that 

 much of the water work was done sub- 

 glacially, although there is no proof as yet 

 that such was the case. The main movement 

 of the great ice sheet was south about 6° west, 

 while Kinsman Notch at Lost River runs 

 nearly east and west. It is probable that 

 the ice in Lost River was nearly stationary 

 during the height of glaeiation, and that the 

 main body passed over it with a shearing mo- 

 tion toward the south. The drainage under 

 the ice would follow the present natural slope. 



A study of the ground between Lost River 

 .and the cliff to the north helps to an under- 



standing of what has probably taken place in 

 the river. The way is difficult and somewhat 

 dangerous. Huge blocks of granite are met 

 with at once. They are piled in a pell-mell 

 manner. As one ascends the blocks become 

 somewhat smaller. There has undoubtedly 

 been a large rock fall and one which immedi- 

 ately suggests a heavy earth shock as the start- 

 ing force. Gradual weathering and falling 

 would not account for the manner in which 

 the rocks are wedged together. Weathering 

 on all the large blocks of the rock fall, and on 

 those in the river, has gone, as far as I can 

 judge, to the same extent. From this fact it 

 is also natural to conclude that the faU was of 

 a sudden nature and not gradual. If the 

 blocks had fallen one by one, weathering 

 should have progressed to very different ex- 

 tents in different blocks. The granite of the 

 cliff and that in Lost River is the same. 

 There are no traces of any rock but the local 

 granite in the rock fall, so this immediately 

 does away with any ideas of a lateral moraine. 

 It is very evident from the amount of weath- 

 ering that this rock fall came long ago, and 

 probably soon after the ice of the Glacial 

 Period had retreated from Kinsman Notch. 



It is now plain that most of the blocks in 

 the river came from the sides of the original 

 gorge, and not from the cliff, as I had for- 

 merly thought. Veins and dikes from the solid 

 walls of the gorge can be found frequently in 

 the loose blocks in the river, close to the places 

 whence they were broken off. It is not al- 

 ways possible to say, on account of breakage, 

 from which side of the gorge they came. 



Although most of the blocks in the river 

 came from the gorge itseK, the rock fall from 

 the cliff reaches to the very edge of the river, 

 so it is almost certain that a number of the 

 blocks came from the cliff. Surely the large 

 number suggests more than just those which 

 have fallen from the sides of the gorge. 



That there was a strong earthquake in 

 Kinsman Notch after the Glacial Period, and 

 that this quake was the prime cause of the 

 great rock fall, and of most of the confusion 

 found at present in Lost River, appears likely. 

 The movements of the joint blocks can not 



