Septembeb 13, 1907] 



SCIENCE 



355 



deepen its valley, it fails after a time to 

 supply the lake, which thereupon disappears 

 by evaporation; only to be formed again later 

 when the river, having aggraded its valley, 

 supplies an artificial canal that is led into the 

 ancient lake-bed for irrigation, with the result 

 of forming a small lake in the bottom of the 

 depression. 



Such, in generalized terms, is the impres- 

 sion gained from reading " The topography 

 and geology of the Fayiim province of Egypt," 

 by H. L. Beadnell (Survey Dept. Egypt, Cairo, 

 1905, maps, sections and fine plates). The 

 river is the Nile. The north-sloping upland 

 is "the great undulating high-lying gravelly 

 desert-plateau which stretches with little 

 change of character to the Mediterranean " 

 (p. 15). Its southern margin is the upper- 

 most escarpment (P), Jebel el Qatrani, capped 

 with basalt, which supplies a black talus to the 

 slopes below; it is in these slopes and in those 

 of the next lower escarpment (2V), that the 

 strata have recently (1901) been found to con- 

 tain numerous mammalian fossils, for which 

 Osborn's American Museum party has recently 

 searched (see Science, March 29, 1907). 

 Where the Nile valley cuts the next cuesta 

 (L), the corner of the escarpment stands forth 

 in a commanding bluff, Elwat Hialla, from 

 which one may gain a broad view up and down 

 the river, with Cairo and the Pyramids in 

 the north, the yet higher escarpment of the 

 uplifted desert plateau on the east, and the 

 first of the subsequent basin-depressions to the 

 southwest, holding the oasis of the Eayum, 

 watered by the Bahr el Yusef from 200 kil. 

 up the Nile, and the shallow lake, Birket el 

 Qurun, some 40 kil. long, with its bottom 

 about 50 m. below sea-level ; while the dip plain 

 of the lower limestone (I, Eocene) ascends 

 slowly in the southern distance. In ancient 

 historic times, the depression contained the 

 much larger Lake Moeris, which then served 

 to regulate the flow of the lower Nile; and in 

 still earlier, pre-historic times here stood a 

 similar lake, now recognized by its silts. Ad- 

 ditional small basins occur farther southwest. 

 Still farther away in the same direction, the 

 weak strata rise to " the ordinary desert 



plateau, on which the outcrops of the beds 

 of successive rock stages follow one another 

 in regular order from south to north, but with- 

 out forming well-marked topographic fea- 

 tures " (p. 27) : it is on the strength of this 

 brief statement regarding' the beveling of the 

 rock series that we have inferred the (Mio- 

 cene) peneplanation of the region; possibly 

 an insiifiicient foundation for a broad general- 

 ization. The winds are still effective agents 

 of erosion and transportation; rock ledges are 

 described as wonderfully carved by sand blast 

 (p. 85) ; and long sand-dune windrows are com- 

 mon, a remarkable one being shown in plate 

 XV.; nevertheless, the occasional action of 

 wet-weather streams is evidently dominant in 

 determining the details of the ragged escarp- 

 ments, which repeat bad-land forms, familiar 

 in our western country. 



Whether the generalized statement given 

 above is correct or not, it is not easy to say; 

 for translations from the topographic descrip- 

 tion of an observer acquainted with the ground, 

 into systematic physiographic description by a 

 reviewer who has not seen the ground, is ad- 

 mittedly difficult. There need be no question 

 as to the stratigraphic sequence, for that is 

 set forth in the systematic fashion of estab- 

 lished geological terminology; but the topo- 

 graphic features produced by the work of 

 desert erosion are not described in terms of 

 standardized type forms, hence the translation 

 from empirical to systematic language is 

 somewhat uncertain. 



Shall the linear depressions and reliefs of 

 the Fayum basin and the escarpments to the 

 northwest be called "vales" and "wolds," as 

 suggested by Veatch (see these notes for June 

 14, 1907) ? The ragged escarpments of the 

 cuestas have no likeness to the softly rounded 

 forms of the Lincolnshire and Yorkshire 

 " wolds " ; and the barren misery of the un- 

 irrigated desert depressions is strongly at vari- 

 ance with the connotation of an agreeable 

 landscape, usually suggested by " vale." 



THE ARID CYCLE IN EGYPT 



H. T. Ferrar, lately of the British Ant- 

 arctic expedition and now of the Geological 



