Royal Society. 465 



February 15, 1855. — Thoma3 Bell, Esq., V.P., in the Chair. 



The following communication was read : — 



" An Account of some recent Researches near Cairo, undertaken 

 with the view of throwing light upon the Geological History of the 

 Alluvial Land of Egypt." — Part First. By Leonard Horner, Esq., 

 F.R.SS.L. & E., F.G.S. 



The author commences by observing, that although it be highly 

 improbable that we can ever form an appropriate estimate in years 

 of the age even of the most modern strata, we are not cut off 

 from all hope of being able to assign an amount in years to the 

 duration of some of the great geological changes which, in past 

 ages, the present surface of the earth has undergone, by causes 

 that are still in operation ; especially by a careful study of the 

 formation of the deltas of great rivers, and of the action of the 

 latter on the rocks and soils they traverse in their course. If in 

 a country in which a certain alteration in the land has occurred, we 

 know that such alteration has taken place in part within historical 

 time, and if the entire change under consideration presents through- 

 out a tolerable uniformity of character, we may be justified in 

 holding the portion that has taken place within the historical period 

 to afford a measure of the time occupied in the production of the 

 antecedent part of the same change. 



Egypt supplies us with the earliest evidence of the existence of 

 the human race recorded in works of art ; in its monuments we find 

 the dawn of the historical period and of civilization ; and that land 

 alone, of all parts of the world as yet known to us, offers an instance 

 of a great geological change that has been in progress throughout 

 the whole of the historical period, in its annual inundations and the 

 sediment these deposit to form the alluvial land in the valley of the 

 Nile ; and there is good reason for believing that the change had 

 been going on with the same uniformity for ages prior to that period 

 when our reckoning of historical time begins. To investigate the 

 formation of the alluvial land in the valley of the Nile in Upper and 

 Lower Egypt is therefore an object of the highest interest to the 

 geologist and the historian. 



The author being impressed with the conviction that this geolo- 

 gical problem could only be solved by having shafts and borings 

 made in the alluvial soil to the greatest practicable depths, deter- 

 mined to have some such experiments made ; as the results might 

 lead the way to other researches on a greater scale. The ground on 

 whicli he hoped to be able to form a chronometric scale by which 

 the total depth of sediment reached might be measured, was the 

 same as that on which the French engineers in 1800 had proceeded, 

 viz. the accumulation of Nile sediment around monuments of a 

 known age. If that depth of sediment be divided by the number of 

 centuries that have elapsed since the date of the erection of the mo- 

 nument, we obtain a scale of the secular increase of which the base 

 of the monument is zero, assuming that the average increase from 

 century to century has been uniform within an area of some extent. 



Phil. Mag, S. 4. Vol. 9. No. Gl . June 1855. 2 H 



