MUSEUM OF COMPARATIVE ZOOLOGY. 219 



All the facts in the case serve to indicate that the non-^anitic ma- 

 terial found upon the mountain is a portion of the so-called " northern 

 drift," with the fact of whose distribution — not the manner — we are 

 here concerned. But we may and must suppose that in the distribu- 

 tion the sides and summits of Ktaadn, as far up at least as 4,G00 feet, 

 received deposits of drift more or less in quantity. Through the action 

 of gravitation the slopes have become loaded with fragments of granite 

 that have been wedged from its mass by frost. Ktaadn has thus been 

 buried under its own ruins, and beneath these ruins has been hidden 

 the drift that was deposited when the mountain was comparatively 

 intact. The avalanches which have produced the slides have brought 

 to light along their course the covered drift. Near the starting-point 

 of the descent, where the movement was superficial, little or none of 

 the hidden material has been unearthed ; but farther down, where the 

 avalanche ploughed deep, more was brought to the surface. The shorter 

 East Slide, therefore, which is superficial in comparison with the other, 

 shows far less drift than does the Southwest Slide ; while Avalanche 

 Brook, which flows over the steepest of the lower slopes, reveals in its 

 deep channel more of drift than has elsewhere yet been found upon the 

 whole mountain. There is reason to think that the bed of another 

 stream, that runs on the north side of the East Spur, will, if followed 

 up, yield like testimony. 



But while proofs of the former presence of an ice sheet upon Ktaadn 

 are so scanty and questionable, seeming indications of local glaciation 

 are not wanting. The location and surroundings of three little ponds, 

 that lie just without the mouths of the basins, are at least signifi- 

 cant. Their waters are retained in place by low, irregular ridges, sit- 

 uated just where terminal moraines of glaciers issuing from the basins 

 would naturally occur. Those that hem in the second and third ponds, 

 counting from the outlet of the chain, on the supposition that they are 

 moraines, must have been deposited by glaciers that moved down from 

 the North Basin. The ridges that hold the first pond, and separate it 

 from the second, would seem to have been supplied by a glacier from 

 the South Basin. Entirely satisfactory determination of the nature of 

 these ridges is impossible while they are, as at present, completely masked 

 by dense thickets ; but should fire hereafter lay them bare, opportu- 

 nity will be afibrded for thorough examination before a new growth 

 springs up. 



The outlet of the first or lower pond is cut to the depth of about 

 twelve feet, through a ridge of debris that appears to be the continua- 



