The frontier between these two states was as natural as any can be between two countries. The whole district from the bay of the lesser Syrtis, or the country of Tripoli, is a deep sandy desert, of which only a few parts, the neighbourhood of Tripoli, and the ancient Leptis, are capable of cultivation. But agriculture there being limited to sandy districts, produces nothing but _durra_, the African millet, and palm trees, which succeed in sandy ground, if it is well watered. The desert advances close to the coast, and the inhabitable coast tract is interrupted and unequal. On the east of Leptis, where the desert retreats farther into the interior and around the great Syrtis, the country forms a real sea of sand, which is far more dangerous than the Sahara, where the ground is for the most part firm; on this Syrtis, on the other hand, persons sink deep into the sand at every step. On the frontier there were boundary marks, called _Arae Philaenorum_. The tradition about them was as follows:—Once the Cyreneans and Carthaginians being involved in a dispute about their frontiers, determined to send out men from the two extreme towns of their countries at the same moment, agreeing that the point of their meeting should be the frontier. This tradition is probably an invention, like so many other things which Sallust relates from Punic authorities. The SYRTES are generally described by the ancients, especially by the earlier Greeks, as one only. The Syrtis, they say, has tides, and is a bay full of sand-banks, which are sometimes sufficiently covered with water and sometimes rise above the water like lagoons. The existence of tides in the Mediterranean has, until recently, been denied, and all the statements of the ancients regarding them have been rejected, as in general ancient geography, about thirty or forty years ago, was treated with extreme recklessness. Tides do exist beyond all doubt, but they occur in a very irregular and unaccountable manner. They are very unequal: at Venice you may see it every day, and during a spring tide, the water rises as much as one foot and a half; it also exists in the Archipelago and in the Euripus near Chalcis, where it comes from the north, which has given rise to the story about the death of Aristotle.[76] It is said, that at Naples the tides are not perceptible, but that at Antium they are, especially when there is a spring tide. The peculiarity of the Syrtes, which the ancients asserted, and which moderns have denied, is that a current runs into the Syrtes and thus throws vessels on the sand-banks. This arises from the meetings of two currents, one of which comes from the Adriatic and the other from the Aegean; the one coming from the Euxine encounters that coming from the Ionian sea, and moves round in a curve, as in general all currents of the sea move in curves. We cannot wonder, therefore, that during a north-west wind, ships, sailing from Sicily to the Archipelago,