and the Euphrates, as the four were not seen together. I have introduced them in the place where I saw them, because, first, no optical effect explains any such shift; and, second, they run through and to well- seen spots, which renders it more likely that they are distinct canals.

Between the Euphrates and the Sabaeus Sinus are several canals and spots that show the minute manner in which the Martian surface is cut up. But so much only hints at the state of things existent there. From the markings, not well enough seen to admit of mapping, it is apparent that the system of lines and spots is very complete all over the planet.

This brings us back again to the Sabaeus Sinus and the Fastigium Aryn, from which we set out, after a journey which it takes the rotation of the planet twenty-four hours thirty-seven minutes and about twenty- three seconds to accomplish.

III. Seas

With the so-called seas, however, the case is different. Several important facts conspire to throw grave doubt, and worse, upon their aquatic character. To begin with, they are of every grade of tint,--a very curious feature for seas to exhibit, unless they were everywhere but a few feet deep; which again is a most singular characteristic for seas that cover hundreds of thousands of square miles in extent,--seas, that is, as big as the Bay of Bengal. The Martian surface would have to be amazingly flat for this to be possible. We know it to be relatively flat, but to be as flat as all this would seem to pass the bounds of credible simplicity. Here also Professor W. H. Pickering's polariscope investigations come in with effect, for he found the light from the supposed seas to show no trace of polarization. Hence these were probably not water.

In parenthesis we may here take notice of the absence of a certain phenomenon whose presence, apparently, should follow upon water surfaces such as the so-called seas would offer us, Although its absence is not perhaps definitive as to their marine character, it is certainly curious, and worth noting. If a planet were covered by a sheet of water, that water surface would, mirror-like, reflect the sun in one more or less definite spot. Looked at from a distance, this spot would, were it bright enough, be seen as a high light on the dark background of the ocean about it. It would seem to be a fixed star at a certain point on the disk, the surface features rotating under it. The necessary position is easily calculated, and this shows that parts of the so-called seas, especially at oppositions like the last one, pass under the point. There remains merely the question of sufficient brilliancy in the spot for visibility; but as in the case of Mars its brilliancy should be equal to that of a star of the first magnitude, it would seem brilliant enough to be seen. No such starlike effect in such position has ever been noticed coming from the blue-green regions. From this bit of negative evidence, to be taken for what it is worth, we return again to what there is of a positive sort.

Not only do different parts of the so-called seas contrast in tint with one another, but the same part of the same sea varies in tint at different times. Schiaparelli noticed that, at successive oppositions, the same sea showed different degrees of darkness, and he suggested that the change in tone was dependent in some way upon the Martian seasons.

Observations at Flagstaff have demonstrated this to be the case, for it has been possible to see the tints occur consecutively. In consequence, we know not only that changes take place on the surface of