Study of the New York Obelisk as a Decayed Boulder. 105 



rounded altered blocks," and Delesse also states/ "Near the cata- 

 ract, the separated blocks of syenite have sometimes a spheroidal 

 form, and they disintegrate iu concentric layers." Lieut. Newbold 

 also reports:^ "The granite of Egypt is freer from the decay, the 

 maladie da granit, than that of India, arising probably from the 

 peculiarly dr}' atmosphere of Egypt, which has been mainly instru- 

 mental in preserving, almost in their original freshness, its magnifi- 

 cent sculptures and vivid frescoes." 



As to the climate, however, there is abundant evidence of past 

 exaggeration of its arid character, and of the occurrence of heavy 

 falls of rain, though at long intervals, as well as of the constant 

 heavy dews. These render it certain that the action of water in 

 erosion, infiltration, and hydration has ever played a slow but 

 important part in effecting decay of the rock in that region. 



For example, Lepsius relates, in his account of travel through 

 Egypt, that he encountered at Assouan a violent thunder-storm, 

 with heavy rain, which afterwards rolled down the Nile valley for 

 nearly 600 miles, as far as Cairo. ^ 



Concerning the Libyan hills, Ebers also states:* "From time to 

 time — rarely indeed, and in most cases only once a year, in the 

 winter months — dark storm-clouds gather around the heads of the 

 mountains; and soon the rain pours down with such violence, on 

 the hill country, that it seems as if all the collected vapors of the 

 year were being restored to the earth in one tremendous torrent. 

 The brooks and cascades that tumble down the rifts and crevices in 

 the mountains collect in the valleys ; the streams form a regular 

 system of little rivers ; and at last, gathering in one main valley, 

 the flood rolls on, either slowly and majestically, or vehemently, 

 ruining all it meets with on its way, till it loses itself in the Red 

 Sea or the Nile." 



Further data on this subject are given beyond, in the notes on 

 the climate of Alexandria (Section 1 1). 



It is also apparent, by a study of views and photographs from 

 this region and of references to its scenery by passing travellers, 

 that the picturesque character of the vicinity of Syene is mainly 

 due to the extent and character of general rock-decomposition 

 which there prevails. Thus Denon,^ in 1802, describes the scenery 



1 Delesse, loc. cit., 488. 2 Newbold, loc. cit., 340. 



* Lepsius, Letters from Egypt, 119. * Ebers, op. cit., II, 333. 



^ Denoii, op. cit., 83. 



Annals N. Y. Acad. Sci., VIII, July, 1893.— 8 



