Popular Science Monthly/Volume 61/September 1902/Areography
THE
POPULAR SCIENCE
MONTHLY
SEPTEMBER, 1902.
| AREOGRAPHY. |
By PERCIVAL LOWELL,
Vidi ego, quod fuerat quondam solidissima tellus
Esse fretum: vidi factas ex acquore terras;
Ovid, Metam, xv., 262.
"What once was solid ground I've seen to be a strait:
Lands I've seen made from out the sea."
HAD Ovid not let Pythagoras say this intentionally of the Earth he might be credited with having meant it for Mars. So startlingly apposite is its application to the history of Martian discovery. For the verse expresses to a presentment the course of man's acquaintance with that planet. A surface supposed at first partly land and sea; the land next seen to be seamed with straits; and lastly the sea made out to be land. Such is the history of the subject, and words could hardly have put the facts more neatly. 'Vidi ego, quod fuerat quondam solidissima tellus esse fretum' sounds like Schiaparelli's own announcement of the discovery of the canals. Indeed I venture to believe he would have made it had he chanced to remember the verse. 'Vidi factas ex acquore terras' certainly sums up what has since been found for the seas.
Three stages mark the course of Martian map-making from its beginning sixty-odd years ago to the present day. They constitute three epochs in the subject, which may be recognized distinctly in the chain of successive charts made of the surface of the planet from then till now. Such a series, however, is not for most people obtainable. Only to specialists is the evidence for or against any scientific belief present at any time in its entirety. Not only has the new evidence not had time to filter through the usual channels into general absorption, but the old too has often remained either unknown or ignored, buried in the books which nobody reads. Thus the whole chain of argument is rarely available to those not engaged in the investigation, and the conclusions reached appear to hang on slenderer threads than is really the case. It has seemed to me, therefore, not without profit to collect into one the various views of the cartography of Mars, so much, that is, as is essentially original and not mainly confirmative of the work of previous observers. To this intent, I have produced the new maps, reproduced the old and set them opposite one another. Thus brought face to face they make a rather impressive self-confessed avowal of relationship.
Twelve maps constitute the series. Each marks the point areography had reached at the time. No map has been left out which added anything new except when a contemporary added more. The twelve maps arranged in chronological order are these:
| I. | Beer and Mädler, | 1840. |
| II. | Kaiser, | 1864. |
| III. | Dawes by Proctor, | 1867. |
| IV. | Résumé by Flammarion of all to date, | 1876. |
| V. | Schiaparelli, | 1877. |
| VI. | " | 1879. |
| VII. | " | 1882. |
| VIII. | " | 1884. |
| IX. | Lowell, | 1894. |
| X. | " | 1897. |
| XI. | " | 1899. |
| XII. | " | 1901. |
As is commonly the case when things are summed up, much more results than one anticipates. It always turns out that one has spent more than he imagines; and fortunately with accumulations it is sometimes the same. Much emerges thus from the present assemblage and three points in particular stand out to command attention. The three points will be found to be:
1. The fundamental agreement of the whole series.
2. Evidence that the peculiarity of the markings seen by Schiaparelli was not the fathering of fancy, but a recognition forced upon him by the markings themselves.
3. A visible evolution in discovery which has steadily progressed from the beginning to the present day marked by three stages—pre-Schiaparellian, Schiaparellian and what we have learned since.
To be struck by these three deductions it is only necessary to compare the several maps with one another when one shall have learnt so much of the circumstances of each as to make their relations understandable.
The first map ever constructed of Mars was drawn by Beer and Mädler in the fortieth year of the last century, and is here numbered I. The observations upon which it was based were made with a four inch telescope and extended in all over eight years. In this map all the main features which we note to-day are unmistakably depicted. The 'Eye of Mars' (the Lake of the Sun) is well seen, as well as the
dark marking that makes eyebrow to it on the south. Next come the Mare Sirenum and the Mare Cimmerium as one long leech-like patch, duly inclined to the parallels. Then follows the Syrtis Major, the first discerned of all the markings on the planet. It was drawn by Huyghens in 1659. Out of it is delineated the Icarium Mare, ending unmistakably in the Sabaæus Sinus seen as a scroll. Dark patches to the south
stand for the Mare Erythræum and sporadic ones in the midst of the great continental areas north give adumbration of the canals and oases later to be discovered there.
The next map, No. II., is Kaiser's, made in 1864. In it it is easy to trace all the fundamental features we have noted in the chart of Beer and Mädler: the Eye, the Maria, the Syrtis Major, the Sabæus Sinus. In general they perfectly reproduce their prototypes, while in detail they present a little more closely the appearance of the same
markings to-day. The map is a slight advance upon its predecessor, and a complete corroboration of it. In these portraitures Kaiser stood not alone. About the same date Lockyer, although he constructed
no map, made some excellent drawings quite confirmative of Kaiser's and rather better. So also did Dawes (Map III.), nicknamed the eagle-eyed for his ability to detect difficult phenomena.
Schiaparelli opened a new era in 1877 (Map V.). Unsuspicious of what he was to stumble on, he seized the then favorable opposition to make, as he put it, a geodetic survey of the planet's surface. He hoped to find this undertaking feasible to the accuracy of micrometric measurement. His hopes did not belie him. He found that it was
possible to measure his positions with sufficient exactness to make a skeleton map on which to embody the markings in detail—and thus to give his map vertebrate support. But in the course of his work he became aware of hitherto unrecognized traits of the so-called continents.
Instead of displaying a broad unity of face the bright areas appeared to be but groundwork for streaks. The streaks traversed them in all directions, tessellating the continents into a tilework of islands. Such mosaic was not only new, but the fashion of the thing was of a new order or kind. The old markings were patches which might well enough be seas and oceans, but here were narrow bands which could hardly pass muster as straits, so long and narrow were the arms thus thrust out into the continents by the seas. Straits, however, Schiaparelli considered them and gave them the name canali, or channels.
How unfamiliar and seemingly impossible the new detail was is best evidenced by the prompt and unanimous disbelief with which it was met.
I have spoken of Dawes as draughting some of these lines; but it must not be supposed that he did more than adumbrate them. It is
possible now to recognize in what Dawes saw, glimpses of something which later Schiaparelli observed, but it would be quite erroneous to imagine such suggestions as in any sense forestalling a view of the things themselves. Perhaps the best proof of such insufficiency is that Schiaparelli himself was the only person who perceived any relationship between the two, and that after the fact.
Unmoved by the universal scepticism which rewarded his epoch making discovery, Schiaparelli went on, in the judgment of his critics, from bad to worse—for in 1879 (Map VI.) he took up again his scrutiny of the planet to the detecting of yet further peculiarity. He re-observed most of his old canals and discovered half as many more. But the striking part of the affair is something which does not seem to have attracted attention—the increased unnatural look of his lines. Lost in the general incredulity a little bizarreness more or less escaped significant criticism. It was all so strange that any change in strangeness simply went to confirm the universal skepticism.
In 1881-2 (Map VII.) he attacked the planet again and with results yet farther out of the common. His lines were still there with more beside, but the startling thing about them was their appearance. If they had looked strange before, they now appeared positively unnatural. The things were simply fine, narrow, uniform, straight lines sometimes alone, sometimes astoundingly paired, but, however associated, geometrical to a degree. As he himself expressed it, they seemed as if drawn by rule and compass, these absolutely regular lines connecting one dark marking with another.
In 1883-4 (Map VIII.) the same thing occurred. An unnatural precision distinguished all his 'canali' To add to the difficulty of acceptance, as in 1882, they followed arcs of great circles, and were in every respect markings of a highly suspicious cast of character. Nor did his exclusive perception of them conduce in astronomic estimation to the assurance of their objective existence.
The map compiled from the observations of 1883-4 was the last made by Schiaparelli of the whole planet. In subsequent oppositions the south pole was so tilted away from the earth that only the regions of the northern hemisphere were well seen and in consequence charted. But the omissions are not material to the present purpose, for the character of the charting remains substantially the same.
As will have been gathered from the above description, the factitious appearance of the 'canals' was the chief bar to their acceptance. That they looked inconceivable argued their conception in the brain of the observer alone. An inference, this, not without a certain justification in the inability of others to follow in his steps. But one point contained in the charts failed of making its impression. If we compare with special reference to the unnaturalness of the lines the several maps of the series with one another we shall be aware of a progressive increase in regularity in the physiognomy of the canals with the time. Schiaparelli's map of 1877 viewed in the light of his subsequent productions seems but a tame bit of innovation after all. His canals as he saw them then were narrow winding streaks, hardly even roughly regular and by no means such departures from plausibility as to be without the scientific expurgatorial pale. Indeed to a modern reader prepared beforehand for geometric construction they will probably appear no 'canals' at all.
Certainly the price of acceptance was not a large one to pay. But like that of the Sybilline books it increased with putting off. What he offered the public in 1879 was much more dearly to be bought. The lines were straighter, narrower and in every way less natural than they had seemed two years before. They were again refused belief and on seemingly better grounds. In 1881-2 they progressed still more in unaccountability. They had now become regular rule and compass lines as straight, as even and as precise as any draughtsman could wish and quite what astronomic faith did not desire. Having thus donned the character, they nevermore put it off. Their precision grew persistent until finally other men began to admit what on much easier terms they had earlier rejected.
Now this curious evolution in design points to one interesting deduction. It shows that Schiaparelli started with no preconceived idea on the subject. On the contrary it is clear that he shared to begin with the' prevailing hesitancy to accept anything out of the ordinary. Nor did he overcome his reluctance except as by degrees he was compelled, for the canals did not change their characteristics nor could the glimpse he got of them have altered as time went on, except in frequency, so far as the eye itself was concerned. But the brain made different account of the reports as it grew familiar with the messages sent it, and gradually by acquaintance learned to distinguish more particularly what it saw. In other words, the geometrical character of the 'canals' was forced upon him by the things themselves instead of being, as his critics took for granted, foisted on them by him. We have since seen the regularity of the canals so undeniably that we are not now in need of such inferential support to help us to the truth, but too late, as it is, to be of controversial moment the deduction is none the less of some historic force.
The year 1890 brought Schiaparelli's labors to a close; and 1892 ushered in at once a new cycle of the planet's seasons and a fresh set of observers on earth. In 1892 the planet was again favorably placed for observation, much as it had been in 1877, and the chief observers of it were W. H. Pickering at Arequipa, Peru, and Schaeberle and Barnard at the Lick Observatory, California. Just as Dawes had made in some sort a transition between the first period and the second, so these observers furnished the stepping stone from the second period to the third. W. H. Pickering detected in the planet 's dark regions certain yet darker ramifications which he denominated river-systems. Nearly simultaneously the Lick observers noted what they called streaks in the same regions. These markings were as their names imply irregular or indeterminate. Nor were they credited by their discoverers with
significance beyond what the names import. They were thus of the same transition character as Dawes' delineations. But Pickering drew some important inferences from what he saw. From what he detected
he concluded that the greater part of these dark areas could not be seas as they had been supposed to be even by Schiaparelli. Schaeberle and Barnard on this and on other grounds advanced something of the same theory.
In 1894 (Map IX.) Douglass at Flagstaff discovered a fact which did for the dark regions what Schiaparelli's canals had done for the light ones. He found on scrutinizing the southern dark areas that Pickering's river-systems, which he too had seen in 1892, came out
again and proved to be but part and parcel of a systematic set of lines networking those areas. He noted that these lines were not only simple streaks, but that they had nothing irregular about them, and could not possibly, therefore, be the river-systems supposed by Pickering. The lines were straight, equable in width and connected with one another at
certain determinate points. They followed apparently arcs of great circles and covered all the dark regions which could be well seen with a singularly symmetric mesh. In other words, they presented all those strange, peculiar and enigmatic characteristics which distinguished the so-called canals, and rendered them unlike anything else in heaven and earth. Here was a fact of the utmost significance. The curious canal system was not confined to the bright regions of the planet. The dark regions, too, had a canal constitution as intricate and as complete as theirs and its perfect parallel.
It is interesting to note that the dawning recognition of these canals followed the same course that it had with the others. Both sets were perceived as streaks and sinuousities before their strangely regular character flashed upon the observer.
As time went on it became evident that the two sets of canals formed part of one whole. The mesh in the bright regions ended at points on the so-called coast-line where the mesh in the dark regions began. The system was thus knit together and made of a piece over the whole surface of the planet. On the belt of narrow 'seas' lying between the continent and the chain of islands to the south, it was as of a lacing run through eyelets in the coast-lines giving an effect of slashed trunk-hose, so singularly did the canals criss-cross them working up in a zigzag progression from one end of a sea to the other.
In 1896-7 (Map X.) the dark region canals came out still more distinctly and especially the oases or spots at their junctions.
At the succeeding oppositions they continued visible and the few dark areas in the northern hemisphere were found in 1899 (Map XL) and still more so in 1901 (Map. XII.) to be similarly but groundwork for a superposed mesh of knots and netting. No part of the somber portions any more than of the light ones remained free of the systematic triangulation.
Furthermore each period contains within itself a progressive development in particularity. Each successive opposition has made the foundation it found more secure and added a superstructure of its own. And what has been true of each period by itself has been equally so of the three taken together. As the maps show, each has been at once a review and an advance. This has been due not only to increased optical facilities and improved atmospheric conditions, but still more to systematic, persistent and extended work on the part of the observers.
It will thus be seen that three stages mark the advance in areography from the time of Beer and Mädler to the present day and that these stages are distinguished by the detection of essentially new and fundamental phenomena:
| I. | Stage of supposed continents and seas. |
| II. | Stage of 'canals' found intersecting the lands. |
| III. | Stage of 'canals' found traversing the 'seas.' |
Each of the stages is here represented by four maps, and each is an advance upon its predecessor.