106 Study of the New York Ohelialc as a Decayed Boulder. 



near the First Cataract: "These mountains, all bristling with 

 black and sharp projections, cast their sombre reflections in the 

 waters of the stream. . . . After passing the cataracts, the rocks 

 grow loftier, and, on their summit, blocks of granite are heaped up, 

 appearing to cluster together and to hang in equipoise, as if with 

 the purpose of producing the most picturesque effects. Through 

 these rough and rugged forms, the e}-e all at once discovers the 

 magnificent monuments of the Island of Philae." Miss Amelia B. 

 Edwards' also refers to the same scene : " Perhaps the most entirely 

 curious and unaccustomed features in all this scene are the moun- 

 tains. . . . Other mountains are homogeneous and thrust them- 

 selves up from below in masses suggestive of primitive disruption 

 and upheaval. These seem to lie upon the surface foundationless; 

 rock loosely piled on rock, boulder on boulder ; like stupendous 

 cairns, the work of demi-gods and giants. Here and there, on shelf 

 or summit, a huge rounded mass, many tons in weight, hangs 

 poised capriciously." 



The peculiar features which mark an extensive, deep and long 

 continued deca}' of rock in place are well shown in the accompany- 

 ing illustration, from a photograph made by my friend. Dr. H. 

 Carrington Bolton, of a granite-cliff about 2 miles south of Syene 

 (PI. IV). We have here all the indications of a slow decay, progress- 

 ing most rapidly along the planes of bedding andjointage, also eating 

 out the latent lines of shrinkage and weakness, and so dividing the 

 whole mass into angular fragments, with slight adherence, only 

 remaining in place by gravity, like the Ijoulders in a stone-wall. 

 Exfoliation has parth' rounded the angular blocks at their corners 

 and edges, even in position ; while those on the crest, and those 

 that have rolled out into full exposure to sun and to night-radia- 

 tion, have been largely rounded off into true boulder form. 



[At this point a series of recent photographs was exhibited, in- 

 cluding the following: View of the First Cataract from the S.W., 

 with deeply etched and roughened boulders and tops of columns, 

 on the crest of the cliff in the foreground : View of an old watch- 

 tower near Syene, showing horizontal bedding and strong joints 

 in the cliff, and several well rounded boulders, with surface scaling 

 off in successive coats : Frith's view of Philae, from the head of the 

 cataract, on the north, showing the deep erosion of the strong joints, 



1 Edwards, op. cit., 231. 



