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



and high polish of its first execution on its north and east faces ; 

 but the minute particles of sand with which the air is charged, in 

 passing over the desert, have entirely defaced its south and west 

 sides, by beating against it during the 1600 years in which it has 

 stood in its present position.'" 



In favor of this view is the fact of the greater injury on the 

 present S.S.W. and W.N.W. sides, those which fronted the K ham- 

 seen, which, in Egypt, blows at intervals from the S. and S.W., 

 driving fine sand, though seldom for more than a day in duration.' 



But, even on these sides of the shaft, the deepest injury is at the 

 upper part of the W.S.W. corner, most out of reach of flying sand, 

 and of a different character from the superficial erosion effected by 

 that agency. It was only during the last few centuries that the 

 obelisks have been exposed to sand at Alexandria, having been 

 previously protected within the wall of the city; while, at An, the 

 sands of the desert have never reached their site. 



The excellent condition of the partially sand-enveloped obelisks 

 of Thothmes I and of Hatasu at Karnak, and of Rameses II at 

 Luxor, show how limited is the erosion attributable to this agencv, 

 as well as to the heat of the sun, on Syene granite, during long 

 periods. 



(d). Disintegration by nitrous efflorescence. Injurious action of 

 this origin was noticed in 1809 by Hamilton,^ on sandstone from 

 the quarries at Hadjar Silsilis: "The rock, in which these quarries 

 have been excavated, is a very uniform, compact granular sand- 

 stone, enclosing sometimes ligneous petrifactions. It is extremely 

 hard when exposed to a dry climate and a warm sun, but easily 

 softened by rain, so as to be damaged when moist by whatever 

 touches it too rudely. The exterior of those temples which have 

 been built of it preserves a very clear sandy color ; but the walls 

 of the inner apartments are blackened by the confined damps, and 

 by the action of the nitre with which the air is impregnated. In 

 these rooms, the surface of the stone is easily detached in thin 

 flakes." 



In his study of the Great Temple at Karnak, Mariette-Bey 

 observed, in 1875: " Every year the river penetrates it by infiltra- 

 tion, and, uniting with the saltpetre with which the soil is impreg- 



1 Osburn, op. cit., 49. 2 Rawlinson, Hist. Anc. Eg., I, 46. 



" Hamilton, op. cit., 85. 



