7. Of one marvel of this sea-coast, namely the “dug mullets,” we have already spoken; we will now mention another, even more surprising. Between Marseilles and the outlets of the Rhone there is a circular plain, about 100 stadia distant from the sea, and about 100 stadia in diameter. It has received the name of the Stony Plain, from the circumstance of its being covered with stones the size of the fist, from beneath which an abundant herbage springs up for the pasturage of cattle. In the midst of it are water, salt-springs, and salt. The whole both of this district and that above it is exposed to the wind, but in this plain the black north,[1357] a violent and horrible wind, rages especially: for they say that sometimes the stones are swept and rolled along, and men hurled from their carriages and stripped both of their arms and garments by the force of the tempest. Aristotle tells us that these stones being cast up by the earthquakes designated _brastai_,[1358] and falling on the surface of the earth, roll into the hollow places of the districts; but Posidonius, that the place was formerly a lake, which being congealed during a violent agitation, became divided into numerous stones, like river pebbles or the stones by the sea-shore, which they resemble both as to smoothness, size, and appearance. Such are the causes assigned by these two [writers]; however, neither of their opinions is credible,[1359] for these stones could neither have thus accumulated of themselves, nor yet have been formed by congealed moisture, but necessarily from the fragments of large stones shattered by frequent convulsions. Æschylus having, however, learnt of the difficulty of accounting for it, or having been so informed by another, has explained it away as a myth. He makes Prometheus utter the following, whilst directing Hercules the road from the Caucasus to the Hesperides: “There you will come to the undaunted army of the Ligurians, where, resistless though you be, sure am I you will not worst them in battle; for it is fated that there your darts shall fail you; nor will you be able to take up a stone from the ground, since the country consists of soft mould; but Jupiter, beholding your distress, will compassionate you, and overshadowing the earth with a cloud, he will cause it to hail round stones, which you hurling against the Ligurian army, will soon put them to flight!”[1360]