MUSEUM OF COMPARATIVE ZOOLOGY. 221 



was, or was not, the track of veritable glaciers of a former period, it is now 

 occupied at intervals by moving masses that approach as nearly to the 

 character of glaciers as changed climatic conditions permit. The hollow 

 is so broad, comparatively shallow, and smoothly concave in outline, 

 that it cannot have been fiishioned by running water, which on Ktaadii 

 leaves its mark always in deep and narrow gorges. At al)Out the mid- 

 dle of the concavity an open strip, ten or twelve rods wide, and com- 

 pletely cleared of trees, runs down the slope, for more than a mile from 

 the bare upper mountain, through thick woods below. The growth, at 

 the intermediate point where we struck the strip, is one of spruces 

 twenty feet high, that rise like a wall on either side of the square-cut 

 opening; while the strip itself is covered with growing bushes that 

 averaged, last September, less than five feet high. Among the bushes 

 lay prostrate, with their tops pointing down hill, small spruce trunks, 

 bleached and dry, and evidently for some years dead. None of them 

 were more than ten feet long. The dead trunks had been simply 

 broken near the ground, and still lay attached to or near their bases. 

 That the movement which cleared the strip is one that occurs only at 

 intervals of some years, is proved by the considerable size the trunks 

 had attained before they were broken down ; and that at least one 

 descent had taken place since that which felled them is shown by the 

 fact that the eastern border of the strip, for a width of two rods, was 

 free from bushes, but was covered with levelled spruces as large as those 

 of the adjacent wood, and still retaining their branches and bark in 

 nearly fresh condition. Here the thickness of the trunks was so great 

 that they were not broken, but the roots were torn from the scanty 

 soil on the upper side, leaving in the earth those that extended in 

 the downhill direction. The mass that last descended was two rods 

 wider on the east than any other which for many years had passed 

 down the path. It must have levelled, for the time being, the bushes, 

 whose elasticity saved them from breaking, and restored them to the 

 upright position. 



The inclination of the hollow, thi-ough its wooded portion, is mod- 

 erate for Ktaadn. It is evident that snow, accumulated on the bare 

 and steeper slopes above, under conditions that have recurred only after 

 periods of some years, has swept down as an avalanche with an impetus 

 that bore it far over the forest-obstructed smaller slope below.* In 



* Under peculiar conditions, a trifling slope may serve, not only for the transmis- 

 sion, but for the origin of an avalanche. In Augusta a street, 1 00 feet wide, runs 

 west from the river directly up the terraces before described to the general level 



