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 Ausonia at the south with Libya to the north, Libya being upon the equator. This region (Plate XII.) is interesting as having been the scene of great changes at previous oppositions. There used to be a spot, the Lake Moeris, in the midst of it, joined by the Nepenthes—the canal running east and west about eight degrees north of the equator—to the Syrtis Major, the great dark gulf somewhat to the west of the central meridian in the picture. Latterly the Syrtia Major seems to have encroached upon Libya, and, at the last opposition, only the faintest glimpses could be got of Lake Moeris, which showed chiefly as a bay of the Syrtis Major itself. Here, as elsewhere, I use aquatic names with terrestrial understanding.

Parallel in a general way to the Nepenthes, and about as much below it as it is below the coast-line, lies the Astapus, which joins the bottom of the Syrtis Major to the ends of the Amenthes, Lethes, and Achelous.

In Plate XIII. two features are striking, both not far from central on time disk,—the lower, the Syrtis Major; the tipper, Hellas. The Syrtis Major was the first marking to be certainly recognized on Mars. It appears in a drawing by Huyghens made on October 13, 1659, the first drawing of Mars worthy the name ever made by man, and reproduced on