1088 Appendix II: Phytogeography and Geology. 
Mean Vapour Tension. 
Loeality d|/8) ele) 3 g/elslaiele sts 
Sle lel 4S (5 \s14/a/s jaja le 
Cairo. . .| 7.2| 7.8] 7.8] 8.7! 9.9| 11.9] 13.6 14.6| 14.9] 13.2| 10.6| 8.1/ 10.6 
Giza. . .| 72| 74| 84| 10.2| 11.6] 13.4] 15.1| 15.8] 15.6] 14.3] 10.8] 8.3| 11.6. 
Aswan . .| 64| 7.2} 68] 7.2} 8.4/10..| 10.4| 11.3| 12.8] 13.0| 10.0| 7.7| 93 
Assint . .| 5.9| 5.3/5.6) 74| 7.7| 84| 7.8 7.4} 9.1] 9.5] 7.3] 67| 73 
On leaving Aswan the river flows due north in a narrow valley 
hardly more than a kilometre wide and bounded by sandstone 
cliffs about 20—30 metres high; behind this the desert rises slowly 
till on the west about 20—30 kilometres distant the steep face of 
the cretaceous limestone cliffs in seen bounding the higher desert 
plateau. At Gebel Silsile the Nile flows through a comperatively 
narrow channel 350 metres wide and many writers have maintained 
that there was formerly a rocky barrier at this point which the 
river has in time removed. There is but little change in the 
geographical character of the valley until near Beni Suef when the 
limestone plateau bends back so as to include the depression of 
the Faytim afterwards passing under later deposits and not again 
appearing on this side. 
The general dimensions of the valley are shown in the following 
table’). 
width 
Loeahity Kilometres ai a0 i ~ | Between cliffs 
UY f y ee of River of alluvial plain 
rom Aswan 
metres | kilometres kilometres 
ASWEN «ioe \s 0 800 —_ 2.8 
lichard aaa le 110 800 6.4 8 
Wuksor os as 219 1250 1.9 12.5 
GET re athe! veph a 264 750 11.5 15 
Warshiites tee. 355 1200 10.5 13 
Solero ge = 448 450 15 18 
AGBIUE. -., > us 549 900 10 12 
Welltwi' ven. bo" 650 850 16 22 
inves! eat 700 1000 11.5 17 
Meshinejean cess 792 1000 13 17 
Beni Suef. . . 826 1500 21 24 
Al-Myat . alm. 895 800 7.5 9.5 
CRILO. .  eeae te ie 945 600 15 17 
The Nile between Aswan and Cairo follows a depression in 
which it has gradually deposited a considerable thickness of alluvial 
1) Lyons: The Physiography of the River Nile and its basin. — Cairo 1906. 
