FEATURES OF AMES KNOB 203 



The relation of relief to these rock masses is direct. The yielding 

 sediments are cut down to a 2)lain, nearly to sealevel, from the southern 

 edge of which the compact andesite rises in a steep bluff about 140 feet 

 high. From the summit to the east, south, and west profiles descend on 

 gentle and roughly uniform slopes of andesilic lava, flattening as they 

 approach the shore, and the irregularities which break their uniformity 

 appear from a distance to be fortuitous effects occasioned by very local 

 variations in the rocks. On nearer view, however, the details of form 

 are found to be significant of conditions of sculpture. 



DETAILS OF FORM 



The steep northern slope of Ames knob has already been referred to. 

 It is in effect a cliff, the upper portion of which is bare rock, while the 

 lower slope, consisting largely of talus, is covered with trees. It is illus- 

 trated in plate 17, figure 1, and the rounded form of the summit, due to 

 glaciation, is strikingly apparent. Strongly contrasting with the profile 

 shown in this view is that on the southern side of the knob, as it appears 

 in plate 17, figure 2. Here we see a cliff, approximately 40 feet high, 

 rising from a sloping bench, which is broken by ridges of rock and 

 strewn with large angular fragments. The altitude of this bench at the 

 base of the cliff is 80 feet above sea. It extends northeastward, south, 

 and southwestward to distances varying from 150 to 200 yards from the 

 base of the summit knob, and its outer margin is marked here and there 

 by prominent ledges rising from 8 to 5 feet or more above the grassy 

 slope. Their altitude is approximately 60 feet above sea, but probably 

 varies 5 or 10 feet either way from this amount. The bench enclosed 

 between them and the base of the highest pinnacle is a much gentler 

 slope than that above or below, and in any profile drawn southward 

 from the summit of Ames knob to the shore it appears as the base of a 

 distinct reentrant angle. That it is not due to a weak layer in the other- 

 wise massive rocks is apparent from the character of the numerous out- 

 cropping ledges, which are practically uniform in hardness with the 

 summit. Glaciation has played an important part in modifying the 

 landscape forms of the region, and one might interpret this bench as an 

 effect of ice sculpture, such as we find where a small glacier lingers on 

 a mountain side after the retreat of the general ice-sheet ; but such 

 effects are produced in the shadow of a hill, and this slope is exposed 

 to all the force of the southern and southwestern sun. There are many 

 instances on these islands of plucked ledges — that is, ledges whose south- 

 eastern or southern face is a surface from which blocks have been torn b}^ 

 the advancing ice, leaving steep jointed faces exposed. The southward- 



