substantially the same size throughout. As to whether the lines are even on their edges or not, I should not like to say; but the better they are seen, the more even they look. It is not possible to affirm positively on the point, as they are practically nearer one dimension than two.

On the other hand, their length is usually great, and in cases enormous. A thousand or fifteen hundred miles may be considered about the average. The Ganges, for example, which is not a long one as Martian canals go, is about 1,450 miles in length. The Brontes, one of the newly discovered, radiating from the Gulf of the Titans, extends over 2,400 miles; while, among really long ones, the Eumenides, with its continuation the Orcus, the two being in truth one line, measures 3,540 miles from the point where it leaves the Phoenix Lake to the point where it enters the Trivium Charontis,--throughout this whole distance, nearly equal to the diameter of the planet, deviating neither to the right nor to the left from the great circle upon which it set out. On the other hand, the shortest line is the Nectar, which is only about 250 miles in length; sweetness being, according to Schiaparelli its christener, as short-lived on Mars as elsewhere.

That, with very few exceptions, the lines all follow arcs of great circles is proved,--first, by the fact that, when not too long, they show as straight lines; second, that, when seen near this limb, they appear curved, in keeping with the curvature of a spherical surface viewed obliquely; third, that, when the several parts of some of the longer lines are plotted upon a globe, they turn out to lie in one great circle. Apparent straightness throughout is only possible in comparatively short lines. For a very long arc upon the surface of a revolving globe tilted toward the observer to appear straight it, or its prolongation, must pass through the centre of the disk at the moment. Such, of course, is rarely the case. At times, however, the conditions are strikingly fulfilled by the great canal called the Titan. The Titan starts from the Gulf of the Titans, in south latitude 20 degrees, and runs north almost exactly upon the 169th meridian for an immense distance. I have followed it over 2,300 miles down the disk to about 43 degrees north, as far as the tilt of the planet's axis would permit. As the rotation of the planet swings it round, it passes the central meridian of the disk simultaneously throughout its length, and at that moment comes out so strikingly straight it seems a substantialized meridian itself.

Although each line is the arc of a great circle, the direction taken by this great circle may be any whatsoever. The Titan, as we have seen runs nearly due north and south. Certain canals crossing this run, on the contrary, almost due east and west. There are others again, belting the disk at well-nigh every angle between these two extremes. Nor is there any preponderance, apparently, for one direction as against any other. This indifference to direction is important as showing that the rotation of the planet has no bearing upon the inclination of the canals.

But, singular as each line looks to be by itself, it is the systematic network of the whole that is most amazing. Each line not only goes with wonderful directness from one point to another, but at this latter spot it contrives to meet, exactly, another line which has come with like directness from quite a different direction. Nor do two only manage thus to rendezvous. Three, four, five, and even seven will similarly fall in on the same spot,--a gregariousness which, to a greater or less extent, finds effective possibility all over the surface of the planet. The disk is simply a network of such intersections. Sometimes a canal goes only from one intersection to another; more commonly it starts with right of continuation, and, after reaching the first rendezvous, goes on in unchanged course to several more.

The result is that the whole of the great reddish-ochre portions of the planet is cut up into a series of spherical triangles of all possible sizes and shapes. What their number may be lies quite beyond the possibility of count at present; for the better our own air, the more of them are visible. About four times as many as are down on Schiaparelli's chart of the same regions have been seen at Flagstaff. But, before proceeding further with a description of these Martian phenomena, the history of their discovery deserves to be sketched here, since it is as strange as the canals themselves.

The first hint the world had of their existence was when Schiaparelli saw some of the lines in 1877, now eighteen years ago. The world, however, was anything but prepared for the revelation, and, when he