NOTES 331 



says with justice that if the point of the river could be ascertained 

 where the rise begins the question would be settled. He does 

 not appear to have known much about the river, for he believed 

 that the water is for the first time collected into a single channel 

 at Philae. In his account of that place and of the cataract 

 there (168, 169), he speaks of the river's egress from Ethiopia, 

 and of deserts which are crossed by the trade route to the Red 

 Sea. In a subsequent part of the treatise he gives the inter- 

 esting and important information that he had himself seen and 

 conversed with two centurions who had been despatched by Nero 

 to discover the source of the Nile (235). From them he learnt 

 that they had penetrated far into the heart of Africa, and had 

 reached a region of illimitable marshes where the river was so 

 covered and impeded with vegetation that neither on foot nor by 

 boat could it be ascended. There can be no doubt that these 

 enterprising explorers had come to the sudd, which in recent 

 years has been found so serious an impediment to navigation. 

 They informed Seneca that in the marsh region they had seen 

 with their own eyes " two rocks from which an enormous body 

 of the river came out." There are apparently no rocks along 

 the course of the Nile in the present marsh region, which is a 

 vast flat, and it is therefore difficult to conjecture to what the 

 two military surveyors allude. Possibly they saw the mouth of 

 some affluent of the main stream such as the Khor Adar, or the 

 sudd may have extended further north than it does now. 



Seneca's account of the Nile derived from travellers and 

 previous writers gives a clear summary of what was then known 

 about the river, but of more interest is his discussion of the 

 opinions that had been propounded before his time as to the 

 cause of the annual rise. He first quotes the view of Anaxagoras, 

 shared by the Greek tragedians and widely accepted, that this 

 rise was due to the melting of snow on the uplands of Ethiopia. 

 This idea he cogently combats by adducing various kinds of 

 evidence of the great warmth of the climate in those southern 

 regions. Some of these proofs, indeed, are exaggerations, as where 

 he affirms that silver is unsoldered or melted. But one of his 

 proofs, drawn from the habits of the animals of the country, is 

 worthy of notice. He remarks that no hibernating creature is 

 found there, and that even in midwinter the serpent is seen above 

 ground. He argues that in Africa, as in Europe, melting snow 

 would swell the rivers in spring and early summer, whereas the 

 Nile flood continues to rise later during four months. 



In a subsequent part of this treatise (235) allusion is made to 

 an explanation which had been given of the rise of the Nile, that 

 it is due not to the fall of rain from above but to the outflow of 



