August 17, 1888.] 



SCIENCE. 



83 



•ocean. They are in general two or three thousand miles in length, 

 though sometimes much longer, by from perhaps thirty to one hun- 

 dred and fifty miles in breadth. They are generally arranged in 

 pairs two or three hundred miles apart, drawn on the arcs of great 

 circles, and so exactly parallel that usually no deviation can be de- 

 tected. They run in all directions, but there are about a dozen 

 points which seem marked as special centres from which they radi- 

 ate. Thus ten start from the Trivium Charontis as a centre, and 

 eight from the Lacus Phoenicis. They cut up the continental sur- 

 face of the planet so that there is no spot more than four hundred 

 miles distant from one of these markings. They are usually so 

 fine that no color can be assigned to them, and they can be merely 

 spoken of as dark lines ; but in a few instances where they broaden 

 out, as in the Lyrtis Major (if this conspicuous marking can be con- 

 sidered one of them), they are decidedly darker than the oceans, 

 and of a grayish or perhaps greenish tint. 



Of a well-defined canal called by Schiaparelli, Hades, M. Perrotin 

 {Annales de I'Observ. de Nice, c. 58) remarks, " Since our first ob- 

 servations, the canal LN has suffered a considerable change : we 

 can distinguish it no longer save to a feeble e.Ktent on the side 

 marked N. Though drawn on the map of M. Schiaparelli of 1S82, 

 this canal does not exist on that of 1879. Our observations, then, not 

 only confirm the changes already stated, but they show further that 

 these changes may be produced in a short period of time." Other 

 evidences of change have since been observed. It is thought that a 

 large portion of the red region known as Libya had changed to 

 green, and afterwards in part back to red. But the latest evidence 

 of change, according to M. Perrotin (Coinptes Rendtis, cvi. 1718, and 

 cvii. 161), is the carrying of several of the so-called 'canals ' across 

 the northern ocean up to the polar ice-cap. If the observation is 

 correct, it is clear that either the ocean is not an ocean, or the 

 canals are not canals. If the observation were confirmed, I should 

 be inclined to deny both propositions. Indeed, the northern ocean 

 as represented by M. Perrotin at this point is but little more than 

 an enlarged canal, while M. Schiaparelli does not indicate it at all 

 upon his maps. 



The latter has thought that many of these canals appear only for 

 a short time, and then disappear again ; and some of them he has 

 only seen shortly after the passage of the vernal equinox on Mars, 

 and thinks that there may be some relation between the two. 



To every argument as to the inherent improbability of an hy- 

 pothesis made with regard to a remote planet, we may be met by 

 the statement that under different conditions these very things may 

 happen, — a statement easily made, and hard to refute. The best 

 we can do, however, is to reason by means of the laws which we 

 have found to apply in the case of the earth. Certainly no such 

 straight canals could be made here naturally, and, if they were 

 made, they would soon be filled up again. If, on the other hand, 

 the canals were artificial, what could be the use of making them so 

 wide,, why arrange them always in duplicate, and why fill certain of 

 them up every year, later to be re-opened .' Think of the labor in- 

 volved in covering over, and then re-opening, a canal, say, sixty 

 miles wide by three thousand miles long, and all in the space of a 

 few weeks. Moreover, in the case of those which are sufficiently 

 ' wide for us to see distinctly, why should the color be so much 



darker than that of the neighboring oceans ? 



Mr. R. A. Proctor has suggested {Monthly Notices Roy. Ast. Soc, 

 xlviii. 307) that the canals are the diffraction-images of rivers pro- 

 duced by mist which hangs over the river-beds. To this sugges- 

 tion, however, some of the same objections apply as to the other. 



M. Fizeau's suggestion {Comptes Rendits, cvi. 1759), that the 

 stripes are cracks between huge masses of ice, presents some diffi- 

 culty in accounting for the red color of the ice ; and also, as was 

 pointed out by M. Flammarion {Comptcs Reiidus,c\'\\. 19), since the 

 temperature of Mars as indicated by the size of the polar spots, is, 

 if any thing, higher than that of the earth, it is surprising that the 

 ice does not melt. 



Before going further let us see what is the probability that these 

 supposed markings are really genuine. Several astronomers, — 

 Dawes, Perly, Burton, and others — have independently constructed 

 maps of Mars, or made observations from which such maps could 

 be constructed ; and it is found, on comparison, that a number of 

 these stripes are common to several of the maps. It is therefore 



probable that these particular stripes are really there. M. Perrotin 

 has confirmed the doubling of the stripes previously mapped by M. 

 Schiaparelli : it is therefore quite possible that these are genuine also, 

 although the observation is one of extreme difficulty, requiring the 

 steadiest possible atmospheric conditions. But the statement that 

 a change in the markings has been observed is one that must be 

 received with extreme caution, and, although a most interesting 

 one, must for this very reason be only accepted as proved, when con- 

 firmed by observations made with the most powerful telescopes at 

 our disposal, and under the most favorable circumstances. 



Starting out from the generally accepted fact that there are 

 stripes upon the planet, we find there are five possible hypotheses to 

 explain their existence. Three, that they are due to water in the va- 

 porous, liquid, or solid condition, we have already noticed. Fourth, we 

 may explain them by supposing them to depend on the color of the 

 rock or soil, and that their shape depends on some peculiar geologi- 

 cal formation. We have, to be sure, no such formations upon our 

 globe ; but we have something analogous, though on a somewhat 

 smaller scale, upon the moon. There we find numerous long nar- 

 row streaks radiating from the crater Tycho, as also in a lesser de- 

 gree from some of the other craters. The streaks are perfectly 

 straight, of very light color, and in a few cases we find them ar- 

 ranged parallel to one another. 



As to the color of Mars, it is probable that the earth would ap- 

 pear of the same color as seen from a distance, if deprived of its 

 vegetation, owing to the red color of its soil in most parts of the 

 world, particularly in the warmer regions. 



If it can be shown, however, that at certain seasons the stripes 

 on Mars really disappear, through some other cause than that of 

 passing clouds or haze in its own atmosphere, then this hypothesis, 

 like that of the water-canals, must fail. 



The fifth and last of the possible explanations is that the stripes 

 are due to differences in vegetation. Whether the stripes indicate 

 vegetation, and the rest is a barren waste, or whether a large pro- 

 portion of the vegetation of Mars is of a reddish color, as suggested 

 by Lambert among others, and approaches in tint toour coleusand 

 autumn leaves, is a matter of no consequence at present. If it can 

 be shown that the stripes on Mars really change, this will be the 

 hypothesis that we shall be forced to adopt, or, rather, we should 

 say it is the only one left presenting no serious improbabilities. 



Let us now review the already ascertained facts with regard to 

 the planet. We are reasonably certain that the surface of Mars is 

 composed of land and water; that it has snow at its poles, and 

 therefore an atmosphere containing clouds. As the snow does not 

 extend over the whole planet, but varies in extent at different times, 

 and what are apparently clouds have been observed in other regions 

 of its surface, it is probable that they likewise have rain. Their 

 temperature cannot be very different from ours, judging by the ex- 

 tent of the snow at the poles, which is rather less in proportion 

 than with us, and has in some instances been known to entirely 

 disappear. Their days are but forty minutes longer than ours ; and 

 their seasons, owing to the inclination of the axis of Mars, are prac- 

 tically the same. The most marked difference between the two 

 planets, of which we are certain, is, that, owing to the lesser attrac- 

 tion of Mars, bodies there would weigh but two-fifths as much as with 

 us : a man, for instance, weighing one hundred and sixty pounds 

 here, would weigh but sixty-four pounds upon Mars. All the con- 

 ditions as far as we can determine, save that their sunlight is some- 

 what weaker, are as favorable to the growth of organic hfe there as 

 here. 



The spectroscope teaches us that the same elements are found 

 throughout the universe : therefore, if we define vegetable life as 

 consisting of organized structures absorbing carbonic acid and giving 

 out oxygen, it will be seen that the admission that vegetable Ufe 

 exists upon Mars carries with it animal life also as a corollary, or 

 vegetation would soon cease for lack of fresh air. 



As Mars is a smaller planet than the earth, and more remote 

 from the sun, it probably reached a suitable temperature to support 

 organic life at an earlier date. The laws of evolution have there- 

 fore had sufficient time to develop reasonably highly organized ani- 

 mal as well as vegetable life. 



This is as far as we are justified in carrying our hypothesis, un- 

 supported by other facts ; but now let us give rein to our fancy for 



