434 



DELTA OF THE NILE 



[Ch. XVIII 



esemblan 



mica 



24-25 ; carbonate of lime, 3-85 ; peroxide of iron, 13-65, & c . 

 It was shown by recent borings, which will presently be 

 mentioned, to be very generally devoid of stratification, ex- 



mar 



blown quartzose sand from the adjacent deserts, so as to 



alternations of sand and loam in thin layers. It is 



cause 



also stated that around Cairo, where artificial excavations 

 have been made, or in other places where the river has un- 



it 



dermined its banks, the 



ferent colours, each of them not exceeding a sheet of thin 



pasteboard in thickness. 



Mr 



ireneral absence of 



Horner 



must be indistinguishable from it. 



U indication of successive deposition 

 might be attributed to the extreme thinness of the layer of 

 matter annually thrown down on the greater part of the 

 alluvial plain. The tenuity of this layer is such as not to 

 average, according to the best observers, six inches in a 

 century. The new superficial deposit, which is added to a 

 soil already softened by a submergence of several months, 



" " " Deep shrinkage cracks 



are formed both hi the new and old soil, where they have 

 been exposed to a hot sun, and into these is drifted dust, 

 raised in clouds by the winds. The action also of worms, 

 insects, and the roots of plants, must be added to these dis- 

 turbing causes, so that it is evident that no distinction can 

 be left between the deposits of two successive years, even 

 at points where the labours of the agriculturist have not in- 

 tervened to annihilate all lines of separation. 



mts of Egypt carry us 



monum 

 more 



equally authentic memorials yet known in other lands, it is 

 there, if anywhere, that we may hope to obtain data for esti- 



" number of years which have 



mating roughly at least the 



amoun 



of change m 



the alluvial plain of a great river. . 



Herodotus observes, 'that the country round Menip i 



■m 





,l!l-j 



*< 



rt 





®f 



" 



1 





r 



if 



even? f 

 bich ha 



Mr- B 



that th 



alluvial ] 

 tiiiebu 



base rf 



tatue i 

 chronoin 



wit ha 



ft 



riouslv t 



their e: 



an ezeai 



of the i 



§ 



^ 



H witi 



at: 

 k a 



e 



H be 



01 



m 



ofgi 



.in 







1 



