In this emergency it might seem at first as if the polar cap of the opposite hemisphere offered itself as a possible reservoir for the momentarily superfluous fluid. But such hoped-for outlet to the problem is at once closed by the simple fact that when the lightening of the dark regions of the southern hemisphere takes place, the opposite polar cap has already attained its maximum; in fact, has already begun to melt. It, therefore, absolutely refuses to lend itself to any such service. This was not known to Schiaparelli’s time, the observations which have established it, by recording more completely the history of the cap, having since been made. Indeed, it was not known even at the time when the writer, in 1894, showed the impossibility of the transfer on other grounds; to wit, on the fact of no commensurate concomitant darkening of the surface elsewhere and on the manifest non-complicity, if not impotency, of the Martian atmosphere in the process. The transference of the water to other dark patches in the northern hemisphere fails of sufficiency of explanation because of the limited extent of such areas on that side of the globe; while the air is quite as incapable of carrying away any such body of liquid, though the whole of it were at the saturation-point, not to mention that there exists no sign of the attempt. The reader will find this reasoning set forth in Mars, published eleven years ago. He will now note, from what has been said above about the northern polar cap, that continued observations since have resulted in opening up another line of proof which has only strengthened the conclusion there reached.
Lines in dark area.
The coup de grâce, however, to the old belief was given when the surface of the dark areas was found to be traversed by permanent lines by Pickering and Douglass. Continued observation showed these lines to be unchangeable in place. Now permanent lines cannot exist on bodies of water, and in consequence the idea that what we looked on there were water surfaces had to be abandoned.
Thus we now know that the markings on both the Moon and Mars which have been called maria are not in reality seas. Yet we shall do well still to keep the old-fashioned sonorous names, Mare Erythraeum, Mare Sirenum, and their fellows, because it is inconvenient to change; while, if we please, we may see in their consecrated Latin couching the fit embalming in a dead language of a conception that itself is dead.
CHAPTER XI
VEGETATION
Since closer acquaintance takes from the maria their character of seas, we are led to inquire again into their constitution. Now, when we set ourselves to consider to what such appearances could be due we note something besides sea, which forms a large part of our earth’s surface, and would have very much what we suppose the latter’s aspect from afar to be, not only in tone, but in tint. This something is vegetation. Seen from a height and mellowed by atmospheric distance, great forests lose their green to become themselves ultramarine.
To dispossess a previous conception is difficult, but so soon as we have put the idea of seas out of our heads a vegetal explanation proves to satisfy the phenomena, even at first glance, better than water surfaces. In their color, blue-green, the dark areas exactly typify the distant look of our own forests; whereas we are not at all sure that seas would. From color alone we are more justified in deeming them vegetal than marine. But the moment we go farther into the matter the more certain we become of being upon the right road. With increased detection the markings they reveal and the metamorphoses they undergo, while pointing away from water, point as directly to vegetation. All the inexplicabilities which the supposition of water involves find instant solution on the theory of vegetal growth. The non-balancing of the areas of shading in their shift from one part of the disk to another, no longer becomes a circumstance impossible to explain, but a necessary consequence of their new-found character, denoting the time necessary for vegetation to sprout. The change of hue of vast areas from blue-green to ochre no longer presupposes the bodily transference of thousands of tons of substance, but the quiet turning of the leaf under autumnal frosts. Even the fact that they occupy those regions most fitted by figure to contain oceans fits in with the same conception. For that the Martian equivalents of forest and moorland, tree and grass, should grow now in the lowest parts of the planet’s surface is what might not unreasonably be expected from the very fact of their being low, since what remained of the water would tend both on the surface and in the air to drain into them.
