the successive presentations of its chief features, and so impressively as to bring Mars-at least in the cartographical sense-within the familiar acquaintance of all who lend him their attention.

As a contribution to science, this pleasant and clever work can scarcely be taken quite seriously. The views it embodies may be summarized as follows: There is no water on Mars, except what is set free by the alternate melting of the snow-caps in the early summer of their respective hemispheres. The dusky areas previously mistaken for seas are really forests or prairies, while the bright parts of the disc represent deserts. Both are cov ered by a vast and intricate network of watercourses, constructed for purposes of irrigation by a powerful, laborious, and intelligent race of beings. The "canals," however, are only visible to us through the verdure lining their shores. They meet in "oases," rescued with incredible toil from the surrounding Sahara-plains, and artificially fertilized. Under these circumstances, it is easy to believe that the polar inundation-the beneficent Nile-flood of a desiccated planet-is the great vital event of each Martian year, its effects being traceable downward over the disc in a connected sequence of seasonal changes.

of Mars turned, visibly grew and dwindled with the alternations of summer and winter. Water, then, it was argued, certainly exists in Mars, and it must cover surfaces sufficiently extensive to supply, by rapid evaporation, the snowy deposits by turns removed and restored. Where were such surfaces to be found unless in the dusky green patches relieved against the ruddy background of what were doubtless Martian continents? These patches were proved, by the experience of two centuries, to be fundamentally permanent. It was no cloud scenery, like that of Venus, with which Mars presented astronomers, but a genuine configuration of land and water. In Mars, as a rule,

The pavilion of heaven is bare. Clouds are scarce, and it is uncertain whether it ever rains in summer. The presence of an atmosphere, however, is in no way doubtful. The wasting of the white calottes alone asserts it with convincing emphasis, since aqueous circulation cannot be maintained apart from atmospheric agency. The "all-sustaining air" employed in the process is thin and translucent, yet efficacious for the discharge of its proper functions. One of the most important of these is the storage of heat. In vain the sun pours in supplies unless a planet does its part by keeping, diffusing, and husbanding them. Now the thermal income of Mars is less than half that of the earth, and its theoretical mean tem

tention than would otherwise have been paid to them. We believe, however, that the world constructed upon the basis afforded by them could under no circumstances prove to be a going concern.

account its low "albedo," or reflective power per unit of area-thirty degrees Centigrade below freezing. Its actual climate is, nevertheless, of a perfectly mild type; the polar snows melt rapidly, and almost completely; nearer to the equator frigid conditions are either wholly absent or so rare that a terrestrial visitant might spare himself the trouble of putting up his skates. Blizzards are unknown; no cyclones carry devastation at express speed across land and sea; the Martian

Thus the composition of the Martian atmosphere must be peculiar. Its ameliorating effects upon climate suggest the presence of some ingredient acting more powerfully than even water-vapor in trapping sunbeams. It contains, indeed, water-vapor besides, as in the nature of things it must, and as the spectroscope states that it does, but not in sufficient quantities to produce the observed effects. The aërial clothing of Mars is obviously quite slight. Except near the edges of the disc, where the eye penetrates obliquely through its layers, it does not sensibly impede vision. Contrariwise, a spectator placed outside the earth might learn something of meteorology, but next to nothing of geography. An occasional star-like flash from a snow-peak, when sunlight struck it at such an angle as to be directly reflected to the watcher outside, would be his sole intimation that a solid surface lay beneath the rolling clouds of luminous haze spread before him. Martian air is commonly estimated to be of only one-seventh the density of terrestrial air. We should have to ascend to twice the height of Mount Everest to meet rarefaction comparable with that prevailing at the level of the "Hour-glass Sea." Under these circumstances, the whole surface of the planet should virtually be situated high above our line of perpetual snow; no open water could, at any season, be found upon it; it should be frost-bound from pole to pole. Since things are in reality far otherwise, we perceive, again from this point of view, that a factor is missing in our calculation, and that factor may be most readily supplied by attributing a special quality to the Martian air. It is well to remember that if barometric pressure be in fact of no more than four and a half inches of mercury-corresponding to oneseventh of an atmosphere-water must boil in Mars at 115° instead of 212°. Evaporation would thus be immensely facilitated, and extensive sheets of water would at times probably dry up with remarkable rapidity.

This may help to explain certain fluctuations of shore-lines noticed with continually increasing rapidity.

The seas of Mars cover about onethird of his surface, and resemble those of the earth in being situated predominantly in his southern hemisphere. Thus, the southern snow-cap is completely encircled by a great body of water, which spreads, with its outliers and tributaries, down to and beyond the equator; while the northern snow-cap is formed on a polar continent. The domestic econnomy of Mars is regulated after a fashion which would scarcely strike us as unfamiliar. His year, indeed, runs on to six hundred and eighty-seven of our days, but day and night alternate at almost the same rate as here; and, since his axis of rotation is but slightly more tilted than that of the earth, his seasons, although comprised in a longer cycle, proceed on the same geometrical plan. They are, besides being protracted, much more unequal than ours, owing to the conspicuous ovalness of the Martian orbit; and it may be added that, according to th astronomical theory of an Ice Age, the southern hemisphere of Mars ought to be strongly glaciated. The requisite conditions are, in fact, present in a more pronounced degree than they could ever have attained to on our globe; yet, somehow, the spell does not work-the southern is to the ful' as warm as the northern hemisphere.

A new epoch in the investigation of Mars was opened by Signor Schiaparelli's discovery of the "canals" of Mars during the memorable opposition of 1877. He may be called a miraculous observer. Everything, so far, seen by him with conviction has had only to wait for full ratification. The views of Mars afforded him by an 83-4 inch, later by an 18-inch refractor were of unprecedented perfection. They had the exquisite clearness of a line-engraving, and left no room for illusion; the features they included were unmistakably there. His canals have thus gradually triumphed over the incredulity, as to

They form a system of extraordinary complexity. At times the reddish areas seem completely enmeshed in fine dark lines. These lines are drawn in accordance with definite laws. In the first place, they trace out great circles of the sphere; they proceed, that is to say, from one point to another by the shortest possible route. Next, they invariably travel from sea to sea, or, at any rate, they put seas in communication with other canals. Each has an evident destination, and never fails to reach it; there is no example on Mars of a Panama Canal. Terrestrial triumphs of engineering are indeed puny performances compared with these other world channellings, which range in length from three hundred to upwards of four thousand miles; in breadth, from eighteen to one hundred and twenty

miles.

Their length and arrangement are constant [Signor Schiaparelli remarks in the paper quoted at the head of this article]1 or vary only between very narrow limits. But the appearance and degree of visibility of all of them change greatly from one opposition to another, and even from one week to another, not simultaneously and according to the same laws, but in most cases, as it would seem, capriciously, or at least in subjection to laws too complex for our unravelment. Often one or two grow indistinct, or even wholly invisible, while others in their vicinity increase to the point of becoming conspicuous with telescopes of moderate power.

Schiaparelli holds it as certain that the "seas" of Mars are true liquid expanses, and the "canals"

simple prolongations of them, crossing the yellow areas or continents. That they are actually great furrows or depressions in the surface of the planet, constituting for

1 We quote with some abridgement and verbal modifications of Professor Pickering's translation.

it a genuine hydrographic system, is demonstrated by the phenomena observed during the melting of the northern snows. These appear at that time surrounded by a dark zone, forming a species of temporary sea. The canals of the encompassing region then grow blacker and wider, increasing so much as to convert, at a certain epoch, the whole yellow region comprised between the edge of the snow and the parallel of 60° North latitude into numerous small islands. This state of things continues until the snow, reduced to its minimum, ceases to melt. Then the canals diminish in breadth, the temporary sea disappears, and the yellow region resumes its original extent. The different phases of these vast phenomena are renewed at each return of the seasons, and we were easily able to observe them in detail during the oppositions of 1882, 1884, and 1886, when the planet presented its north pole to terrestrial spectators. Their simplest and most natural interpretation, by a great inundation due to the melting of the snows, is entirely logical, and in accordance with terrestrial analogy. We conclude, therefore, that the canals are such in fact, and not only in name. The network formed by them was probably determined in its origin at an early stage of the planet's geological history, and has been slowly elaborated in the course of ages.

We learn then that, although the canals are essentially permanent fea tures in Martian topography, they fluctuate notably in aspect. They blacken and widen, often unaccountably, then again grow dim and nebulous, or fade out, perhaps through the drying up of their flowing contents, into the ruddy background. Above all, they undergo, at certain times, the extraordinary metamorphosis "gemination."

called

As the result of a rapid process [we recur to the authority of Schiaparelli] lasting at most a few days, perhaps only a few hours, a given canal is transformed through its entire length into two lines or uniform stripes, which run straight and equal with the exact geometrical precision of the two rails of a railroad. One of these is often superposed as exactly as possible upon the former line, the other being drawn anew, at an interval varying from the least discernible in large tele

scopes-about thirty miles-to three hundred and sixty miles. But in other cases both the lines occupy opposite sides of the former canal, and are located upon entirely fresh ground.

Mr. Lowell is one of the very few observers who have seen to perfection these delicate twin-objects.

In good air [he writes] the phenomenon is quite unmistakable. The two lines are as distinct and as distinctly parallel as possible. No draughtsman could draw them better. They are thoroughly Martian in their mathematical precision. At the very first glance they convey, like all the other details of the canal system, the appearance of artificiality.

At certain seasons, chiefly during the months preceding and following the vernal equinox of the northern hemisphere-in which nearly all the canals are situated-an epidemic of gemination breaks out on this singular little planet. Beginning with sporadic cases in remote districts, it gradually spreads, until, as Schiaparelli has remarked, a grotesque mask of triangulations and double reticulations replaces, for a time, the ordinary configuration of sea and shore. The tendency extends to the lakes at the canal junctions. They appear cut in two by a sort of causeway of ochreous tint, taking invariably the same direction with the debouching double canal. With the canal system is associated a lake system.

Dotted all over the reddish ochre ground of the desert stretches of the planet [Mr. Lowell informs us] are an innumerable number of dark circular or oval spots. They appear, furthermore, always in intimate association with the canals. They constitute so many hubs, to which the canals make spokes. These spots, together with the canals that lead to them, are the only markings to be seen anywhere on the continental regions. Otherwise the great reddish ochre areas are absolutely bare: of that pale, fire-opal hue which marks our own deserts seen from far.

These are his "oases;" there are a "small infinity" of them. Although the leading members of the family were closely studied at Milan, ac

quaintance with it was immensely developed at Arequipa in 1892, and at Flagstaff in 1894. Mr. Lowell's generalization is doubtless correct, that as there are no canal junctions without spots, so there are no spots without canal junctions. On an average, they are from one hundred and twenty to one hundred and fifty miles in diameter; but the great "Lake of the Sun" measures five hundred and forty by three hundred and fifty miles; while the diminutive "Fountain of Youth" is of scarcely appreciable dimensions.

Now the whole system of dark markings on Mars-the seas, the canals, and the lakes-is so evidently one, that only a single rationale of their nature is, in the main, admissible. If the "seas" be indeed aqueous expanses, then water flows in the canals and accumulates in the "lakes." But this is just one of those leading points of Martian doctrine in which belief has been undermined by recent in quiries. The diversities and fluctuations of tint in the greenish areas had long occasioned perplexity. But it was a dormant kind of perplexity, roused into active denial only by som very singular observations made at the Lick Observatory at Arequipa, and at Flagstaff, during the recent pair of oppositions. Not only have the dusky areas shown a mass of minute and intricate detail, but they have been perceived, first by Professor Schaeberle.1 then by Mr. Douglass, to be furrowed by darker lines, corresponding in every respect to Schiaparelli's canals, and bearing, in fact, the semblance of being a continuation of them. Mr. Douglass has even succeeded, with the aid of these enigmatical streaks, in triangulating the principal dark areas, the fluid constitution of which, should his work hold its ground, is thus involved in grave doubt. It appears, indeed, probable that the Gulf Stream, viewed from a great height, through a rare atmosphere, might be traced through the

1 Publications of the Astronomical Society of the Pacific, vol. iv. p. 197.