That Mars is inhabited by beings of some sort or other we may consider as certain as it is uncertain what those beings may be. The theory of the existence of intelligent life on Mars may be likened to the atomic theory in chemistry in that in both we are led to the belief in units which we are alike unable to define. Both theories explain the facts in their respective fields and are the only theories that do, while as to what an atom may resemble we know as little as what a Martian may be like. But the behavior of chemic compounds points to the existence of atoms too small for us to see, and in the same way the aspect and behavior of the Martian markings implies the action of agents too far away to be made out.

But though in neither case can we tell anything of the Bodily form of its unit, we can in both predicate a good deal about their workings. Apart from the general fact of intelligence implied by the geometric character of their constructions, is the evidence as to its degree afforded by the cosmopolitan extent of the action. Girdling their globe and stretching from pole, to pole, the Martian canal system not only embraces their whole world, but is an organized entity. Each canal joins another, which in turn connects with a third, and so on over the entire surface of the planet. This continuity of construction posits a community of interest. Now, when we consider that though not so large as the Earth the world of Mars is one of 4200 miles diameter and therefore containing something like 212,000,000 of square miles, the unity of the process acquires considerable significance. The supposed vast enterprises of the earth look small beside it. None of them but become local in comparison, gigantic as they seem to us to be.

The first thing that is forced on us in conclusion is the necessarily intelligent and non-bellicose character of the community which could thus act as a unit throughout its globe. War is a survival among us from savage times and affects now chiefly the boyish and unthinking element of the nation. The wisest realize that there are better ways for practicing heroism and other and more certain ends of insuring the survival of the fittest. It is something a people outgrow. But whether they consciously practice peace or not, nature in its evolution eventually practices it for them, and after enough of the inhabitants of a globe have killed each other off, the remainder must find it more advantageous to work together for the common good. Whether increasing common sense or increasing necessity was the spur that drove the Martians to this eminently sagacious state we cannot say, but it is certain that reached it they have, and equally certain that if they had not they must all die. When a planet has attained to the age of advancing decrepitude, and the remnant of its water supply resides simply in its polar caps, these can only be effectively tapped for the benefit of the inhabitants when arctic and equatorial peoples are at one. Difference of policy on the question of the all-important water supply means nothing short of death. Isolated communities cannot there be sufficient unto themselves; they must combine to solidarity or perish.

From the fact, therefore, that the reticulated canal system is an elaborate entity embracing the whole planet from one pole to the other, we have not only proof of the world-wide sagacity of its builders, but a very suggestive side-light, to the fact that only a universal necessity such as water could well be its underlying cause.

Possessed of important bearing upon the possibility of life on Mars is the rather recent appreciation that the habitat of both plants and animals is conditioned not by the minimum, nor by the mean temperature of the locality, but by the maximum heat attained in the region. Not only is the minimum thermometric point no determinator of a dead-line, but even a mean temperature does not measure organic capability. The reason for this is that the continuance of the species seems to depend solely upon the possibility of reproduction, and this in turn upon a suitable temperature at the critical period of the plant’s or animal’s career. Contrary to previous ideas on the subject, Merriam found this to be the case with the fauna of the San Francisco Peak region in northern Arizona. The region was peculiarly fitted for a test, because of rising a boreal island of life out of a sub-tropic sea of desert. It thus reproduced along its flanks the conditions of climates farther north, altitude taking the part of latitude, one succeeding another until at the top stood the arctic zone. Merriam showed that the existence of life there was dependent solely upon a sufficiency of warmth at the breeding season. If that were enough the animal or plant propagated its kind, and held its foothold against adverse conditions during the rest of the year. This it did by living during its brief summer and then going into hibernation the balance of the time. Nature in short suspended its functions to a large extent for months together, enabling it to resurrect when the conditions turned.

Hibernation proves thus to be a trait acquired by the organism in consequence of climatic conditions. Like all such it can only be developed in time, since nature is incapable of abrupt transition. An animal suddenly transported from the tropic to a sub-arctic zone will perish, because it has not yet learnt the trick of winter sleeping. While still characterized by seasonal insomnia it is incapable of storing its energies and biding its time. But given time enough to acquire the art, its existence is determined solely by the enjoyment of heat enough at some season to permit of the vital possibility of reproducing its kind.

Diurnal shutting off of the heat affects the process but little, provided the fall be not below freezing at the hottest season. So much is shown by the fauna of our arctic and sub-arctic zones, but still more pertinently to Mars by the zones of the San Francisco Peak region, since the thinner air of altitude, through which a greater amount of heat can radiate off, is there substituted for the thicker one of latitudinally equal isotherms. Here again with the diurnal as before with the seasonal it is the maximum, not the mean, or, till low, even the minimum temperature, that tells.

Now, with Mars the state of things is completely in accord with what is thus demanded for the existence of life. The Martian climate is one of extremes, where considerable heat treads on the heels of great cold. And the one of these two conditions is as certain as the other, as the condition of the planet’s surface shows conclusively. In summer and during the day it must be decidedly hot, certainly well above any possible freezing, a thinner air blanket actually increasing the amount of heat that reaches the surface, though affecting the length of time of its retention unfavorably. The maximum temperature, therefore, cannot be low. The minimum of course is; but as we have just seen, it is the maximum that regulates the possibility of life. In spite, therefore, of a winter probably longer and colder than our own, organic life is not in the least debarred from finding itself there.

Indeed, the conditions appear to be such as to put a premium upon life of a high order. The Martian year being twice as long as our own, the summer is there proportionately extended. Even in the southern hemisphere, the one where the summer is the shortest, it lasts for 158 days, while at the same latitudes our own is but 90 days. This lengthening of the period of reproduction cannot but have an elevating effect upon the organism akin to the prolongation of childhood pointed out by John Fiske as playing so important a part in the evolution of the highest animals. Day and night, on the other hand, alternate there with approximately the same speed as here, and except for what is due to a thinner air covering reproduce our own terrestrial diurnal conditions, which as we saw are not inimical to life.

In this respect, then, Mars proves to be by no means so bad a habitat. It offers another example of how increasing knowledge widens the domain that life may occupy. Just as we have now found organic existence in abyssal depths of sea and in excessive degrees of both heat and cold, so do we find from exploration of our island mountains, which more than any other locality on earth facsimile the Martian surface, its possession there as well.

Another point, too, is worth consideration. In an aging world where the conditions of life have grown more difficult, mentality must characterize more and more its beings in order for them to survive, and would in consequence tend to be evolved. To find, therefore, upon Mars highly intelligent life is what the planet’s state would lead one to expect.

To some people it may seem that the very strangeness of Martian life precludes for it an appeal to human interest. To me this is but a near-sighted view. The less the life there proves a counterpart of our earthly state of things, the more it fires fancy and piques inquiry as to what it be. We all have felt this impulse in our childhood as our ancestors did before us, when they conjured goblins and spirits from the vasty void, and if our energy continue we never cease to feel its force through life. We but exchange, as our years increase, the romance of fiction for the more thrilling romance of fact. As we grow older we demand reality, but so this requisite be fulfilled the stranger the realization the better we are pleased. Perhaps it is the more vivid imagination of youth that enables us all then to dispense with the hall-mark of actuality upon our cherished visions; perhaps a deeper sense of our own oneness with nature as we get on makes us insist upon getting the real thing. Whatever the reason be, certain it is that with the years a narration, no matter how enthralling, takes added hold of us for being true. But though we crave this solid foothold for our conceptions, we yield on that account no jot or tittle of our interest for the unexpected.

Good reason we have for the allurement we feel toward what is least like us. For the wider the separation from the familiar, the greater the parallax the new affords for cosmic comprehension. That which differs little yields little to the knowledge already possessed. Just as a longer base line gives us a better measure of the distance of the sun, so here the more diverse the aspects, the farther back they push the common starting-point and furnish proportionately comprehensive insight into the course by which each came to be what it is. By studying others we learn about ourselves, and though from the remote we learn less easily, we eventually learn the more. Even on the side, then, that touches most men, the personal, the strangeness of the subject should to the far-seeing prove all the greater magnet.

One of the things that makes Mars of such transcendent interest to man is the foresight it affords of the course earthly evolution is to pursue. On our own world we are able only to study our present and our past; in Mars we are able to glimpse, in some sort, our future. Different as the course of life on the two planets undoubtedly has been, the one helps, however imperfectly, to better understanding of the other.

Another, more abstract but no less alluring, appeals to that desire innate in man to know about the cosmos of which he forms a part and which we call by the name of science. Study of Mars responds to this craving both directly by revelation of the secrets of another world and indirectly by the bearing of what we thus learn upon our understanding of the laws of the universe. For the facts thus acquired broaden our conceptions in every branch of science. Some day our own geology, meteorology, and the rest will stand indebted to study of the planet Mars for advance along their respective lines. Already the most alert of those professing them are lending ear to information from this source, and such cosmopolitanism can but increase as the years roll on. Today what we already know is helping to comprehension of another world; in a not distant future we shall be repaid with interest, and what that other world shall have taught us will redound to a better knowledge of our own, and of that cosmos of which the two form part.