Mars other than in the polar cap, and very conspicuous ones too, but that these are due to the changing seasons of the planet's year. We will now see what they look like.

To the transubstantiation of changes of the sort it is a prime essential that the drawings from whose comparison the contrast appears should all have been made by the same person, at the same telescope, under as nearly as possible the same atmospheric conditions, since otherwise the personal equation of the observer, the impersonal inequalities of instruments, and the special atmosphere of the station plays so large a part in the result as to mask that other factor in the case, any change in the planet itself. How easily this masking is accomplished appears from drawings made by different observers of the same Martian features at substantially the same moment. Several interesting specimens of such personal peculiarities may be seen by the curious in Flammarion's admirable thesaurus, "La Planete Mars." In some of these likenesses of the planet it is pretty certain that Mars would never recognize himself.

To have drawings simply swear at one another across a page is, in the interests of deduction, objectionable. For their testimony to be worth having, they must agree to differ. If, therefore, Mars is to be many, his draughtsman must be one. So much, at least, is fulfilled by the drawings in which the changes now to be described are recorded; for they were all made by me, at the same instrument, under the same general atmospheric conditions. As the same personality enters all of them, it stands, as between them, eliminated from all, to increased certainty of deduction. Since, furthermore, the drawings were all made in the months preceding and following one opposition, change due to secular variation is reduced to a minimum. As a matter of fact, the changes are such as to betray their own seasonal character. They constitute a kinematical as opposed to a statical study of the planet's surface.

The changes are much more evident than might be supposed. Indeed, they are quite unmistakable. As for their importance, it need only be said that deduction from them furnishes, in the first place, inference that Mars is a living world, subject to an annual cycle of surface growth, activity, and decay; and shows, in the second place, that this Martian yearly round of life must differ in certain interesting particulars from that which forms our terrestrial experience. The phenomena evidently make part of a definite chain of changes of annual development. So consecutive, and, in their broad characteristics, apparently so regular, are these changes, that I have been able to find corroboration of what appears to be their general scheme in drawings made at a previous opposition. In consequence, I believe it will be possible in future to foretell, with something approaching the certainty of our esteemed weather bureau's prognostications, not indeed what the weather will be on Mars,--for, as we have seen, it is more than doubtful whether Mars has what we call weather to prognosticate,--but the aspect of any part of the planet at any given time.

The changes in appearance now to be chronicled refer, not to the melting of the polar snows, except as such melting forms the necessary preliminary to what follows, but to the subsequent changes in look of the surface itself. To their exposition, however , the polar phenomena become inseparable adjuncts, since they are inevitable ancillaries to the result. With the familiar melting of the snow-cap begins the yearly round of the planet's life. With the melting of our own arctic or antarctic cap might similarly be said to begin the earth's annual activity. But here at the very outset there appears to be one important difference between the two planets. On the earth the relation of the melting of the polar snows to the awakening of surface activity is a case of post hoc simply; on Mars it seems to be a case of propter hoc as well. For, unlike the earth, which has water to spare, and to which, therefore, the unlocking of its polar snows is a matter of no direct economic value, Mars is apparently in straits for the article, and has to draw on its polar reservoir for its annual supply. Upon the melting of its polar cap, and the transference of the water thus annually set free to go its rounds, seem to depend all the seasonal phenomena on the surface of the planet.

The observations upon which this deduction is based extend over a period of nearly six months, from the last day of May to the 22d of November. They cover the regions from the south pole to about latitude forty north. That changes analogous to those recorded, differing, however, in details, occur six Martian months later in the planet's northern hemisphere, is proved by what Schiaparelli has seen; for though the