and some of these may have an important bearing upon the question of the nature of the canals. A glance at Schiaparelli's map shows us the disk of the planet divided into areas of land and water, which are about equal in their total extent. Then crossing the land areas in every direction are the canals, which it will be observed always begin and end either at the edge of a sea, or at a point of junction with other canals. Without varying their direction they cross one another, and in some cases several canals radiate from a single center, which then generally appears expanded into a "lake." In addition there are certain regions which Schiaparelli describes as variable in appearance, or intermediate between the seas and the lands, presenting sometimes the character of maritime surfaces and at other times that of continental areas. Among these are the places marked on the map Deucalionis Eegio, Hellas, and the island called Cimmeria. The region named Libya, which ordinarily appears as a continental expanse, seems to belong to this class of variable areas, and within the past year it has obtained great celebrity because it was said to have been submerged by an inundation from the adjoining sea. This region is more than 200,000 square miles in area, and lies just under the equator. In May last M. Perrotin, of the Nice Observatory, made the somewhat startling announcement that the continent of Libya had disappeared. "Clearly visible two years ago," said M. Perrotin, in his report to the Paris Academy of Sciences, "to-day it no longer exists. The neighboring sea, if sea it is, has completely invaded it. In place of the light reddish tint of the continents of Mars the black, or rather dark-blue, color of the seas has appeared there. . . . In sweeping over the continent the sea has abandoned on the south the region that it formerly occupied, and which now appears with a tint intermediate between that of the continents and that of the seas, a light-blue color, analogous to that of a slightly misty sky in winter."
A look at the accompanying cut will show the change which Perrotin detected. This extraordinary aspect of Libya was first seen in April and lasted into May. In June the "continent" seems to have resumed, or nearly so, its ordinary appearance. Perrotin's suggestion that the change observed was probably periodic appears to be borne out by an examination of former observations of this region of the planet. There was a partial "inundation" of Libya in 1883, and a still more extensive one in 1884, both of which were noted by Schiaparelli, who confirms Perrotin's observation of 1888 in a general way, but does not describe the continent as having at any time completely disappeared. Speaking of its appearance in 1884, Schiaparelli says Libya had a flaky look, as if it had been "covered with innumerable little spots all jumbled together." The suggestion of clouds contained in this