This last conception is clearly derived from the "Isles of the Blest" of the Greeks (originally of the Phœnicians), which were situated in the deep currents of Oceanus and are already referred to in Hesiod.
Seneca, on the other hand, says of the outer limits of the world: "Thus is nature, beyond all things is the ocean, beyond the ocean nothing" ("ita est rerum natura, post omnia oceanus, post oceanum nihil"), and Pliny speaks of the empty space ("inane") that puts an end to the voyage beyond the ocean.
In the year 5 A.D. the emperor Augustus, in connection with Tiberius's expedition to the Elbe, sent a Roman fleet from the Rhine along the coast of Germania; it sailed northward by the land of the Cimbri (Jutland), past its northern extremity (the Skaw), probably into the Cattegat, and perhaps to the Danish islands. Augustus himself, in the Ancyra inscription, tells us of the voyage of this fleet, and says that it came "even to the people of the Cimbri, whither before that time no Roman had penetrated either by land or sea,[82] and the Cimbri and the Charydes (Harudes, Horder), and the Semnones, and other Germanic peoples in those districts sent ambassadors to ask for my friendship and that of the Roman people."[83] Velleius [ii. 106] also gives an account of this voyage, and Pliny [ii. 167] gives the following description of it: "The Northern Ocean has also been in great part traversed; by the orders of the divine Augustus a fleet sailed round Germania to the Cimbrian Cape, and saw therefrom a sea that was immeasurable, or heard that it was so, and came to the Scythian region and to places that were stiff [with cold] from too much moisture. It is therefore very improbable that the seas can run short where there is such superfluity of moisture." Müllenhoff thinks [iv., 1900, p. 45] that on this voyage they saw the Norwegian mountains, the immense "Mons Sævo" (see later under Pliny), rising out of the sea. This is not impossible, but we read nothing about it; nor indeed is it very probable. On the other hand, it is likely that the voyage resulted in fresh knowledge about the North, and that at any rate some of the statements in Mela and Pliny may be derived from this source.