In the East Cyrus, as we saw, had already advanced as far as the Indus; he had conquered the Açvakas on the north of the Cabul, and the Gandaras to the south of that river. Of their neighbours, Bactria and Arachosia had remained true during the great rebellion, though the Sattagydæ (the Gedrosians) had revolted. Darius had himself marched against the Sacæ, and reduced them again to subjection. Herodotus tells us, that he sent out a party to explore the Indus; in which was Scylax, an inhabitant of Caryanda in Caria. They set out from the land of the Pactyes (_i.e._ from Arachosia), and from the city of Caspatyrus (Cabul) they followed the course of the Indus to the sea. Then they sailed to the west, and in the thirtieth month they arrived at the point from which the Phenicians started, who sailed round Africa at the command of Necho (III. 313), _i.e._ they did not return to the Persian Gulf but sailed round Arabia, and landed in the north-west corner of the Arabian Gulf at Heroonpolis. After their return Darius made use of this sea, and subjugated the Indians.[247] The extension of the Persian kingdom in the land of the Indus, by Darius, is beyond a doubt. In the inscription which he caused to be engraved on Mount Behistun after the suppression of the rebellions, he enumerates the nations which obey him. We can find but one name of an Indian nation to the right of the Indus--the Gandaras. The inscription of the palace of Persepolis, which Darius built a few years later, mentions the Idhus, _i.e._ the Indians, besides the Gandarians. Herodotus further informs us that it was the Northern Indians whom Darius had subjugated. They formed the twentieth satrapy of his kingdom, while the Gandarians were united with the Arachoti in the seventh satrapy. The twentieth satrapy of Northern Indians comprised the lands to the north of Cabul, on the right bank of the stream, from the land of the Açvakas as far as the summits of the Himalayas. It paid 360 talents of gold, the highest tax among all the satrapies of the kingdom.[248]