322 THE POPULAR SCIENCE MONTHLY. 



greatest is not comparable in size with any one of the arms of the 

 Nile." After comparing the valley of the Nile with that of the Red 

 Sea (which Herodotus appears not to have visited, and of the magni- 

 tude of which he has a very inadequate conception), he goes on to say : 

 "Now, if the Nile should choose to divert his waters from their present 

 bed into the Arabian Gulf, what is to prevent it from being filled up by 

 the stream within twenty thousand years at most ? For my part, I 

 think it might be filled up in half the time. Why, then, should not a 

 gulf of even much larger size have been filled up in the ages before I 

 was born, by a river which is so large and so given to working changes 

 as the Nile?" 



It is on the strength of these very sound and just physical con- 

 siderations that Herodotus tells us he accepted Egyptian tradition : 



"Thus I gave credit to those from whom I received this account 

 of Egypt, and am myself, moreover, strongly of the same opinion, 

 since I remarked that the country projects into the sea farther than 

 the surrounding shores, and I observed that there were shells upon 

 the hills." Finally, he inquires into the origin of the population of 

 Egypt : 



" I do not believe that the Egyptians came into being at the same 

 time as the delta. I think they have always existed, ever since the 

 human race began. As the land went on increasing, part of the popu- 

 lation came down into the new country, part remained in the old set- 

 tlements." 



Thus Herodotus commits himself to four very definite propositions 

 respecting the unwritten history of Egypt : 



1. That the delta was once an arm of the sea. 



2. That it has been filled up and converted into dry land by the 

 alluvial deposits of the Nile. 



3. That this process of conversion into dry land probably took 

 something like twenty thousand years. 



4. That the Egyptians existed before Lower Egypt, and migrated 

 thence from Upper Egypt. 



And it will be observed that the first three of these propositions at 

 any rate are not mere guesses, but conclusions based upon a process 

 of reasoning from analogy, just as sound in form as any which is to 

 be met with in the discussion of a similar problem in a modern treatise 

 on geology. 



Herodotus wrote twenty-three hundred years ago. In the course of 

 twenty-one out of the twenty-three centuries which have elapsed since 

 hi3 time, I am not aware that any one rose above his level in the discus- 

 sion of such problems as that which he attacked. And some quite mod- 

 ern writers have not yet reached it, for lack of as much knowledge of 

 natural phenomena as Herodotus possessed. Let us look at the facts 

 by the light of such knowledge of elementary physical science as is 

 now happily accessible to every Etonian. 



