The Nile and Diogenes

Lake Victoria, Lake Albert and the
Head Waters of the Nile



It is extremely unlikely that the overwhelming majority of people have heard about the explorer Diogenes who sometime in the first century C.E. was blown off course in the Indian ocean and ended up in the port of Rhapta on the African coast near, or at modernday Dars es-Salaam in modernday Tanzania. 

Either he went inland and explored or local traders told him of two large lakes inland and a range of snow covered mountains from which the Nile had its source. 

The sources are so brief that we have no idea about whether or not Diogenes, whom we know next to nothing about personally, actually made the exploration himself or whether he simply questioned native informants who had seen or heard about the things Diogenes recorded.

Apparently he called the mountain range the ‘Mountains of the Moon” and the melting snow fed two large lakes which in turn fed the Nile. The two streams from the different lakes uniting and that this in turn merged with another river from another lake to form the Nile.

It appears likely that Diogenes or his informants saw or frankly heard about Lakes’ Victoria and Albert which then constitute the two lakes from which streams emerge to unit and form the Nile. The lake and stream that unit with the Nile much further upstream is probably Lake Tsana in Ethiopia and the stream the Blue Nile.1

The Mountain range that Diogenes appears to mention seems to be the Ruwenzori range and perhaps he saw or heard about Mt. Kilimanjaro which was significantly snow capped.2  It does appear that Diogenes greatly exaggerated the size of the range making it 500 miles long when it is in fact much, much shorter. Also it appears that the melting snow is not in fact the source of the Nile’s waters.3

All in all this is quite accurate and it was not until the last half of the 19^th century that Europeans were able to get more accurate information about the Nile’s source.

Sadly we have only one source for Diogenes and it is to put it bluntly both poor and incredibly terse. The only surviving account of the voyage of Diogenes is from the Geographia of Ptolemy written in the mid second century C.E. Ptolemy researched and wrote in the city of Alexandria Egypt and was one of the last significant scholars to work there. Ptolemy didn’t just write the Geographia but he also wrote the Almagest, a text book of Astronomy and a Star Catalogue, which was the basis of Western and Middle Eastern Astronomy for over 1000 years.4 His Geographia is largely a listing of geographical features with estimates of their relative latitude and longitude.5

1. Then, in relation to a voyage between Aromata and Rhapta, a certain Diogenes, he says, returning from the second voyage to India, happened around Aramata, to be driven off course away from the north, and having the Troglodytes on his right arrived after twenty–five days at the swamp from whence the Nile flows, being a little south of the promontory of Rhapta. A certain Theophilus on a voyage to Azania from Rhapta was driven back from the south and on the twentiethday came to Aromata.

2. In neither of these is the actual days of sailing given, but that Theophilus took twenty days and Diogenes twenty five days by sailing around the Troglodytes, only the days on the voyage, not the actual days sailing, or to take account of irregular and alternating winds over so great a span of time – certainly not whether it happened that the voyage was altogether towards the north or towards the south.

3. Just that Diogenes was driven by the north wind while Theophilus was made to give way to the south wind. The remainder of the voyage is understood to have proceeded smoothly, neither of the two has he related in detail. It is incredible that for so many days the wind should have carried so.

4. The voyage of Diogenes from Aramata to the swamps, south of which is the promontory of Rhapta, required twenty–five days and Theophilus from Rhapta to Aramata, a greater distance, took twenty. Theophilus lays down that a day and a night, sailing steadily, amasses about one thousand stadia, (and Marinus follows this reasoning). Nevertheless, Diogenes says that the voyage from Rhapta to Prasum, taking many days and, as calculated, is only five thousand stadia. At the equator the winds being more intractable, because of the sun, change easily and are more treacherous.6 

Later in his Geographia Ptolemy makes references to locations that he seems to have learned from Diogenes.

The junction of the river Nile and the river Astapus (61  12)[Longitude Latitude]

Then the junction of the river Astaboras and the river Astapus (62.30  11.30)

Where the Nile river becomes one through the union of rivers which flows from two lakes. (60  2)

Western Lake (57  south 6)

Eastern Lake (65  south 7)

Coloe Lake from which flows the Astapus river. (69  equator)

…

The entire maritime coast to the Rhaptum promontory is called Azania; the interior region is called Barbaria, in which there are many elephants.7

In another section of the Geographia Ptolemy further describes what appear to be Diogenes’ discoveries.

Aethiopia, which is below this land and entire Libya, is terminated toward the north by the land which we have treated, which extends from the Great bay of the outer sea to Rhaptum promontory as we have said, and is located in (73.50 south 8.25)

Then by a part of the Western ocean which is near the Great bay, by the unknown land toward the west and the south; toward the east by the Barbaricus bay, which is near the shallow sea is called Breve, from the Rhaptum promontory to the Prasum promontory and the unknown land. Prosum promontory moreover is located in (80  south 15)

Near this land is an island toward the east, the name of which is Menuthias; it is located (85  south 12.30)

Around this bay the Anthropophagi Aethiopians dwell and from those toward the west are the Mountains of  the Moon from which the lakes of the Nile receive snow water; they are located at the extreme limits of the mountains of the moon. (57  south 12.30) and (67  south 12.30).8

The above quotes are all we have about the explorations of Diogenes and we cannot be entirely sure that the locations mentioned by Ptolemy in fact were discoveries of Diogenes but that seems to make the most sense. As it is all we have is a few tantalizing hints of what may have been the first detailed exploration of the sources of the Nile. Although it interesting to contemplate that Diogenes in the first century after Christ standing on the shore of lake Victoria watching the Nile flow out. 

1. Cary, M. and Warmington, E. H, The Ancient Explorers, Revised Edition, Penguin Books, London, 1963, pp. 214-215.

2. IBID.

3. IBID.

4. Wikipedia, Ptolemy Here.

5. IBID. 

6. Ptolemy, Geographia Book 1, s. 9, Ptolemy Geographia Books 1 & 2  Here.

7. Ptolemy, The Geography, Book 4, s. 7, Dover, 1991, p. 108. See also Lactus Curtius Here.

8. IBID, Book 4, s. 8, Dover, 1991, p. 109. See also Lactus Curtius Here.

Pierre Cloutier