At all events, the buildings on the island of Philæ demonstrate that the bed of the Nile must have been very much the same as it is now, 2200 years ago; and even a thousand years earlier it must have been the same, if the foundation of the temple on the island of Begh, opposite to Philæ, be near the limit of the highest rise of the Nile of the present time; so that there could be no barrier at the Cataract of Assuan to dam up the Nile when they were constructed; and thus the deafening sound of the waterfall recorded by Cicero and Seneca must still be held to be an exaggeration. The existence of alluvial soil, apparently of the same kind as that deposited by the Nile, in situations above the Cataract of Assuan, at a level considerably above the highest point which the inundations of the river have reached in modern times, to which allusion is made by Professor Lepsius, has been noticed by other travellers, and even at still higher levels than those he mentions. Whether that alluvial soil be identical with, or only resembles the Nile deposit, would require to be determined by a close examination, and especially with regard to organic remains, if any can be found in it. There is no evidence to shew that it was deposited during the historical period, and it may be an evidence of a depression and subsequent elevation of the land antecedent to that period. It may not be of fresh-water origin, but the clay and sand, or till, left by a drift while the land was under the sea. For remote as is the antiquity of Nubia and Egypt, in relation to the existence of the human race, it appears to be of very modern formation in geological time. The greater part of Lower Egypt, probably all the Delta, is of post-pliocene age, and even late in that age; and the very granite of the Cataract of Assuan, that of which the oldest monuments in Egypt are formed, and which, in the earlier days of geology, was looked upon as the very type of the rock on which the oldest strata of the earth were founded, is said to have burst forth during the later tertiary period. We learn from Russegger, that the low land which lies between the Mediterranean and the range of hills that extends from Cairo to the Red Sea at Suez, and of which hills a nummulite limestone constitutes a great part, is composed of a sandstone which he calls a "Meeresdiluvium," a marine diluvial formation, and considers to be of an age younger than that of the sub-appennines.[83] This sandstone he found associated with the granite above Assuan, and covering the cretaceous sandstone far into Nubia. It appears, therefore, that, in the later ages of the tertiary period, this north-eastern part of Africa must have been submerged, and that very energetic plutonic action was going forward in the then bed of the sea. The remarkable fact of the granite bursting through this modern sandstone is thus described by Russegger:--