their separation with telescopes of different apertures, and succeeded in seeing the duplication when both by theory and observation it should have been invisible. Moreover, with a few exceptions, the only drawings he published showing the double canals were made by himself; and these exceptions were mostly made by Douglass, who, in the published text, expressed grave doubts as to the objective reality of the duplication. It is true, several other observers using much smaller telescopes claimed to see it; but it always happened to be just at the limit of visibility of their telescopes, no matter what the size of their instruments chanced to be. One of the most skilful of these observers, M. Antoniadi, later published his doubts as to the genuineness of what he had seen. On the other hand, most of the observers who used large telescopes always saw the canals single. Naturally the astronomers were not convinced.

Now further observations have been male, and new facts brought to light that partially explain this singular phenomenon. According to Professor Lowell, only about one-quarter of all the canals are ever seen to be double, and they are probably double all the time.* It is only when they are very faint that they appear single, and their faintness is apparently the reason that the duplication does not then show. This is due to the fact that under these circumstances one canal is somewhat fainter than the other, and so escapes detection. According to his views, the single canal always coincides in position with one of the two components of the double.

The double canals usually appear, he says, as a broad, hazy band; it is only by glimpses that the duplication is seen. There is nothing improbable in the idea. that one-quarter of the canals should be permanently broad and the rest permanently narrow. The only question is, Is it likely that either the middle of these canals should fade out, leaving the sides dark; or that the sides should darken, leaving the middle bright?

It is a fact that some of the seas, as the season progresses, will fade out across the middle in places, leaving the

*Lowell Observatory Bulletin No. 15.

rest dark, and thus present on a comparatively large scale a phenomenon similar to that claimed for the double canals. This same effect occurs upon the floor of the lunar crater Eratosthenes, forming two widely diverging canals. A long, double canal is also found upon the rim of this crater, but this is clearly due to the presence of two long, parallel cracks. A similar chance occurrence might occasionally be found upon Mars; but it seems to the writer in the light of the facts, and especially of the opinions of Messrs. Douglass and Antoniadi, that the case for a systematic duplication will not be proved until more well-known observ

FIG. 7. MARKINGS on THE SURFACE OF MARS. Drawn by writer from two photographs taken at Flagstaff.

ers, favorably situated and circumstanced, have recorded it.

Seasonal Changes

Perhaps Lowell's most interesting recent investigation is on what he calls the Cartouches of the Canals-that is, their variable visibility dependent on the Martian seasons.* He finds that soon after the beginning of the melting of the northern ice-cap, the canals begin to develop in the north polar regions. These are immediately followed by the canals in the north temperate zone. A few weeks later, those in the torrid zone develop; and still later, those in the south temperate. The process of development, therefore, is carried on across the equator. This is most naturally explained by the growth of vegetation following the annual transference of water from pole

*Lowell Observatory Bulletin No. 12.

from the poles. There are accordingly two fertile and two barren seasons.

Professor Lowell concludes that the water is transferred artificially from pole to pole. In this we can hardly follow him, since with the rare atmosphere, and accordingly rapid evaporation and condensation upon Mars, the aqueous vapor would necessarily flow across the planet's surface of itself, being alternately condensed at each pole by the winter's cold.

A curious feature of the canals and other markings is that they do not always present the same appearance at the same equivalent time in successive Martian years. Thus, a certain marking called by Schiaparelli "Lacus Moris" could not be found at all at Arequipa in 1892. After an interval of thirteen years since it had last been seen, it reappeared with perfect. distinctness in 1903, and was observed by Lowell. A very marked change in the Deucalionis Regio, observed in 1892 in connection with the melting of the icecap, did not take place again at the same equivalent season in 1894; nor has it been observed since. A certain canal observed by Schiaparelli was not found. at all by Lowell, another one having re

*Lowell Observatory Bulletin No. 8.

placed it. This latter only recently disappeared, Schiaparelli's original canal having taken its place.

Is the Planet Inhabited by Intelligent Beings?

There is little doubt now that Mars possesses vegetable, and perhaps animal life; but the question that interests humanity is, Are there intelligent beings there? The only important argument in favor of their existence is the presence of the canals. These canals are so long and narrow, straight and uniform, that they look artificial. If they are artificial, it is certain that their constructors possess a knowledge of spherical trigonometry, and considerable skill in the mechanical construction of surveying instruments, implying greater intelligence than that possessed by our ancestors a thousand years ago. It is doubtful if our progenitors in the year 900 A. D. could have built a perfectly straight road three thousand miles long, directed to a definite point, even if it had been across level country.

But is the evidence sufficient as yet to warrant us in pronouncing in favor of

past few years. It does not seem to him, however, that on either side are they conclusive. The reader must therefore choose for himself between them.

Let us suppose that there are intelligent inhabitants. One can imagine, in the seasonal transfer of the water across the equator, that a portion of the moisture, condensed from the air each night as a heavy dew, is deposited on the ground and perhaps on sparsely growing and therefore invisible vegetation, in the desert regions. From that rare atmosphere, consisting largely of aqueous vapor, so much may be condensed in the

existence of intelligent inhabitants; but without them the canals would almost certainly in the course of time lose their straightness and artificial aspect.

The other explanation of the canals is that they are due to the same causes that produce those on the Moon. As seen through the telescope they look exactly like them, save that the Martian canals are much longer and somewhat wider. The lunar canals seldom exceed ten miles in length. They radiate from small lakes and join large seas precisely like the Martian areas, and are equally straight and artificial looking in appear

The explanation offered is that moisture is given out by the cracks, which is later absorbed. This moisture nourishes the vegetation to which the darkening is due. Exactly similar cracks, causing similar vegetational canals, are found in Hawaii. One characteristic canal was estimated by the writer at two or three

owing to Professor Lowell's indefatigable industry, which will doubtless decide it in time. His observatory is the only one at present specially devoted to securing an answer to it, and it seems almost a pity that some other favorably located observatory should not devote some of its time to the same object.