There were important developments in 1894 other than the founding of the observatory at Flagstaff and the emergence of Percival Lowell as the central figure in the debate over the Martian canals. The spectroscopic detection of water vapor on Mars had been confidently announced in the 1860s and 1870s by William Huggins in England, Jules Janssen in France, and Hermann Vogel in Germany. Janssen's spectroscopic observations in 1867 were especially noteworthy because he had carried his instruments to the summit of 10,741-foot (3,280-m) Mount Etna in Sicily, above much of the lower atmosphere of the Earth, and had noted what seemed to be a definite intensification of the lines caused by water vapor in the spectrum of Mars compared with that of the airless Moon. In 1894 this result was disputed by W. W. Campbell at Lick. With an improved spectroscope attached to the Lick 36-inch (91-cm) refractor in the dry summer air over Mount Hamilton (fig. 13), Campbell found that "the spectrum of Mars . . . appeared to be identical with that of the Moon in every respect."1 The direct evidence of water vapor on Mars had vanished into thin air.
Even more damaging to the Lowellian view of the planet were the observations of Campbell's colleague at Mount Hamilton, Edward Emerson Barnard, who was already well known for the keenness of his sight and the soundness of his judgment. Barnard had overcome great hardships in achieving his leading position in astronomy. He had grown up poor in Nashville, Tennessee, after the Civil War. At the age of nine, after only two months of formal schooling, he had been sent to work in a photograph gallery, where he was assigned the job of keeping a large solar camera used for portrait photography pointed toward the Sun by manually turning a set of large wheels. He was still working at the photograph gallery as a printer and operator when, at the age of nineteen, he received as a surety of a loan a volume of astronomical writings by Rev. Thomas Dick. The book immediately awakened a passion for astronomy in Barnard, and with the help of an older colleague at the photograph gallery, James W. Braid, Barnard put together a small telescope from a simple tube and an old spyglass lens found in the street, which, he later recalled, "looked as if [it] had been chipped out of a tumbler by an Indian in the days of the Mound builders." Nevertheless, this telescope "filled my soul with enthusiasm when I detected the larger lunar mountains and craters, and caught a glimpse of one of the moons of Jupiter."2 By 1877 he had saved enough money to buy a better telescope, a 5-inch (13-cm) refractor, and he studied Mars at the oppositions of that year and, especially, 1879. In 1880, he wrote a small book about the planet, unfortunately never published, which advises an admirable caution in interpreting the observations of the planet:
|It is well to fetter the wings of our fancy and restrain its flights. It is quite possible we may have formed entirely erroneous ideas of what we actually see. The greenish gray patches may not be seas at all, nor the ruddy continents, solid land. Neither may the obscuring patches be clouds of vapor. Man is too quick at forming conclusions. Let him but indistinctly see a thing, or even be undecided as to whether he does actually see it and he will then and there set himself to theorizing, and build immense castles of conjecture on a foundation, of whose existence he is by no means certain.3|
In 1894, with Mars higher in the sky above Mount Hamilton, Barnard obtained more satisfactory observations of the planet. Already in July 1894---three months before opposition---he had begun to obtain breathtaking views of the surface details. On July 23, for instance, with Mare Sirenum in view, he recorded two tantalizing, small dusky spots, which appeared "very feeble and faint when near the middle of [the] disc" but grew black as they drew near the terminator. By early September he was drawing Mars on a scale of 5 inches (13 cm) to the planet's diameter, and watching it from sunset till dawn. The seeing grew exceptionally steady at times, allowing him to use magnifications of more than 1,000x. By now the Solis Lacus region had come into view, and on September 2--3 he recorded in his notebook: "There is a vast amount of detail. . . . I however have failed to see any of Schiaparelli's canals as straight narrow lines. In the regions of some of the canals near Lacus Solis there are details---some of a streaky nature but they are broad, diffused and irregular and under the best conditions could never be taken for the so called canals."5 A week later he had another chance at Mars with the great refractor, but because there was no water in the engines he had to turn the dome and wind the clock drive by hand---"dreadfully hard and exhausting work," he noted.6 The magnificent Hourglass Sea---Schiaparelli's Syrtis Major---was coming onto the disk. The next day Barnard confided to Simon Newcomb:
|I have been watching and drawing the surface of Mars. It is wonderfully full of detail. There is certainly no question about there being mountains and large greatly elevated plateaus. To save my soul I can't believe in the canals as Schiaparelli draws them. I see details where some of his canals are, but they are not straight lines at all. When best seen these details are very irregular and broken up---that is, some of the regions of his canals; I verily believe---for all the verifications---that the canals as depicted by Schiaparelli are a fallacy and that they will be so proved before many oppositions are past.7|
|On several occasions during that summer, principally when the planet was on the meridian shortly after sunrise---at which time the conditions . . . are often exceptionally fine at Mount Hamilton---its surface has shown a wonderful clearness and amount of detail. This detail, however, was so intricate, small, and abundant, that it baffled all attempts to properly delineate it. Though much detail was shown on the bright "continental" regions, the greater amount was visible on the so-called "seas." Under the best conditions these dark regions, which are always shown with smaller telescopes as of nearly uniform shade, broke up into a vast amount of very fine details.8|
|To those, however, who have looked down upon a mountainous country from a considerable elevation, perhaps some conception of the appearance presented by these dark regions may be had. From what I know of the appearance of the country about Mount Hamilton as seen from the observatory, I can imagine that, as viewed from a very great elevation, this region, broken by canyon and slope and ridge, would look just like the surface of these Martian "seas."9|
The last important development during the memorable year 1894 was the publication of a provocative paper by the English astronomer Edward Walter Maunder (fig. 14). As far back as 1879, Maunder had made out, at least in qualified form, some of the Schiaparellian canals, though he had tended to agree with Nathaniel Green's interpretation of them. "Where I have represented shaded districts, [Schiaparelli] has drawn hard lines corresponding with the borders of those districts," Maunder had declared in 1882, "so that where he has given a number of parallel and interlacing lines, I should myself have rather shown faint shaded districts between those lines."10 He now looked at the canal question from a new perspective that went far toward resolving the "canal deadlock."
Born in 1851, the youngest son of a Wesleyan minister, Maunder attended King's College, London, and after graduating worked for a time in a London bank. His real chance came in 1873, when the position of photographic and spectroscopic assistant at the Royal Observatory at Greenwich became vacant. It was to be filled on the basis of performance on a civil service examination, and Maunder scored high enough to get the job. He was assigned to photograph sunspots and measure their areas and positions on the solar disk. In the course of this work he became impressed with the fact that "the smallest portion of the Sun's surface visible by us as a separate entity, even as a mathematical point, is yet really a wide extended area."11 In an article titled "The Tenuity of the Sun's Surroundings," which was published in Knowledge on March 1, 1894, Maunder expanded on this point:
|Now this fact has an important bearing on some of our theories. We easily fall into the mistake of supposing that the most delicate details which we can see really form the ultimate structure of the solar surface; but it is not possible that they can do so. The finest granule, the smallest pore, as we see it, is only the integration of a vast aggregation of details far too delicate for us to detect; and the minute speck of brighter or duller material may, and probably does, contain within itself a wide range of brilliancy, not to speak of varieties of temperature, of pressure, of motion, and of chemical composition.12|
|the rough little experiments to which I have alluded may, I think, throw some light on the "canal system." . . . [A] narrow dark line can be seen when its breadth is far less than the diameter of the smallest visible dot. Further, a line of detached dots will produce the impression of a continuous line, if the dots be too small or too close together for separate vision. There are some intimations that this may be the next phase of the "canal" question, Mr. Gale, of Paddington, New South Wales, having broken up one "canal" into a chain of "lakes" on a night of superb definition, Mars being near the zenith, and Prof. W. H. Pickering, at Arequipa, having under equally favourable circumstances detected a vast number of small "lakes" in the general structure of the "canal system."14|
Though Lowell was later to claim that at Flagstaff, "details invisible at the average observatory were presented at times with copper-plate distinctness, and, what is as vital, the markings were seen hour by hour, day by day, month by month,"16 after he left in November 1894 for Boston and the European tour, conditions at Flagstaff took a turn for the worse. During the winter of 1894--95, A. E. Douglass found "not a single perfect night . . . and scarcely one or two which could be called good,"17 so Lowell decided to cast around for a more favorable climate from which to observe Mars at its next opposition, on December 1, 1896. (While he was abroad in 1895 he is said to have looked closely at several alternative sites, including Pic du Midi in southern France, which, ironically, would later become the site of an observatory famed for its seeing, and the Sahara, where conditions were mediocre at best.)
Meanwhile, he had acquired at a cost of $20,000 a permanent telescope for his observatory---a 24-inch (61-cm) refractor made by Alvan Clark's son, Alvan Graham Clark. It was installed in Flagstaff in August 1896. Since Mars that summer showed a disk only 8" of arc across, Lowell, who by now was back at Flagstaff, tested his new telescope on the inner planets, Mercury and Venus. What he found, though not directly relevant to Mars, had important consequences for the credibility of his Mars observations, and thus deserves at least a brief digression.
Schiaparelli, as we have seen, had assigned a captured rotation to both Mercury and Venus. With his new refractor Lowell found the markings on Mercury so unmistakable that within a day or two he was confident that Schiaparelli had been correct. Lowell also tackled Venus, which despite its brilliance had generally revealed only vague, elusive markings even to the best observers, including Schiaparelli himself. Unexpectedly, Lowell found "many markings" on the nearly full disk.
Lowell rushed into print with his Venus observations, just as he had previously done with his "facts" about Mars.18 His basic description of the planet was unlike anything reported by previous observers. The markings he found there were, he said, "in the matter of contrast as accentuated, in good seeing, as the markings on the Moon and owing to their character much easier to draw. . . . They are rather lines than spots. . . . A large number of them, but by no means all, radiate like spokes from a certain center."19 In late 1896, Lowell moved his telescope and observatory to Tacubaya, near Mexico City, where he hoped to find more favorable conditions for the Martian opposition. Mars produced no new sensations, but the Venusian spoke system continued to hold forth, and Lowell regarded his observations as furnishing final proof of Schiaparelli's earlier tentative announcement that the planet always holds the same face toward the Sun. The observations, he wrote, "may be said to have put the rotation period beyond even reasonable doubt."20
Instead of acquiescence to his views, Lowell found on his return from Mexico in April 1897 that they had met with almost universal incredulity. E. M. Antoniadi, for instance, criticized those who "forgetting that Venus is decently clad in a dense atmospheric mantle, cover what they call the `surface' of the unfortunate planet with the fashionable canal network."21 Meanwhile, Lowell had decided to move the observatory back to Flagstaff, convinced that conditions were not so bad there after all. He had already established his routine of using a diaphragm with his large refractor in order to eliminate the blurring effects of atmospheric eddies swirling overhead. Generally, he found that with a diaphragm cutting the aperture to 12 to 16 inches, "detail which would remian hopelessly hid with the full aperture . . . starts forth to sight."22 This concept was actually less foolish than it may sound; the effects Lowell described are quite real, and they do blur the image in a large telescope.23 Certainly at the time, with the exception of Barnard's after-sunrise observations with the Lick refractor in 1894, large telescopes had yet to demonstrate their effectiveness in planetary work, and on the whole Lowell's ideas about seeing, partly drawn from Pickering's and especially Douglass's investigations, were well in advance of most of his contemporaries.
At this point Lowell suffered "a breakdown of the nerves." He was forced to retreat from astronomy for the next four years, and Douglass became acting director at the observatory. Thus far, he had yet to emerge fully from the shadows of Pickering and Lowell.24 His first priority was to attempt to defend Lowell's observations of Venus and Mars, but he also discovered, in his own right, a set of linelike markings on the Galilean satellites of Jupiter. The markings were immediately criticized by Barnard, who had failed to find anything similar with the refractor at Lick. Douglass's own critical faculties were now aroused, and he began experimenting with artificial planet disks. His confidence was shaken when he found that such disks viewed from a distance of about a mile appeared to have illusory markings that bore an uncomfortable resemblance to some of those reported as occurring on Venus, such as dark faint shadings and cusp caps.25 After Lowell returned to Flagstaff in spring 1901, Douglass rather indiscreetly wrote to Lowell's brother-in-law, William Lowell Putnam, who had served as trustee of the observatory during Lowell's illness, to complain that Lowell's method was "unscientific" and consisted of "hunt[ing] up a few facts in support of some speculation."26 Eventually Lowell learned of the letter, and Douglass was summarily dismissed.
After Douglass left---he went on to found the Steward Observatory at the University of Arizona in Tucson and discovered a lifelong fascination for tree rings---Lowell was briefly left without assistants.27 Before the year was out, however, he was joined first by Vesto Melvin Slipher (Lowell set him to work with a new spectrograph in order to determine the rotation of Venus), and then by Carl Otto Lampland and Vesto's younger brother, Earl Carl Slipher. Apparently Douglass's artificial planet experiments had shaken even Lowell's confidence in the reality of the spokelike markings on Venus, for briefly, in 1902, he published a retraction.28 However, on returning to the telescope in 1903, he found the same spokelike markings staring back at him, "with a definition to convince the beholder of an objectiveness beyond the possibility of illusion."29 He remained convinced of their reality for the rest of his life,30 but in later years he expended relatively little effort in publicly defending them, for he faced a mounting challenge to a much more cherished belief---the reality of the Martian canals themselves.
The year that Lowell recovered the spoke system on Venus, thereby going against the grain of most observers of the planet before and since, Maunder and J. E. Evans made a significant contribution to the canal debate with their paper entitled "Experiments as to the Actuality of the `Canals' of Mars." The paper summarizes the results of an experiment in which boys at the Royal Greenwich Hospital school were asked to reproduce a disk on which no canals had been drawn but only "minute dot-like markings." Maunder and Evans found that when the disk was viewed from a certain distance, the boys drew "canals."31 Lowell, as might be expected, was unimpressed by the "small boy theory" and argued that the canal question ought to be decided not by experiments but by "actual observation directed to that end," expressing confidence that "if England would only send out an expedition to steady air . . . it would soon convince itself of these realities."32
In fact, evidence was mounting that the Martian surface did indeed consist of complex structures lying generally just below the threshold of distinct perception with ordinary telescopes. Among the most remarkable observations in this regard are those made by Percy Braybrooke Molesworth, a captain in the British army stationed at Trincomalee, Ceylon, within only a few degrees of the equator. In 1896, using a 9.25-inch (23-cm) reflector, Molesworth saw more canals than any other member of the British Astronomical Association, but he found them to be broad and curving and entirely lacking in "the hard line-like appearance with which they are drawn by Schiaparelli."33 When he was able to obtain better observations of Mars with a 12.5-inch (32-cm) reflector equipped with a clock drive, in 1903, Molesworth reported that "the amount of detail is bewildering, and I despair of giving even an approximate idea of it in a drawing." Again: "The broad effects one draws are simply the combined results of myriads of small details, too minute to be appreciated separately. . . . I cannot help being certain that our present instruments are quite incapable of dealing with the details of Mars, and that even the best and most careful drawings give an utterly wrong idea of the configuration of his surface. The eye interprets as well as it can, but the task is beyond its power."34 The light and dark areas on Mars appeared to differ only in the tone of the background, since "under the best conditions the maria break up completely. There is no regular shading . . . only a confused mass of streaks, splashes and stipplings of various tones."35
Perhaps the most vigorous advocate of the position that the canals were an illusion produced by smaller unresolved features was the Italian observer Vincenzo Cerulli,36 a man who had studied in Berlin and Bonn, and for a short time had served as assistant at the observatory of the Collegio Romano. Like Lowell, he was a man of independent means, and in 1890 he constructed his own observatory near Teramo, Italy, on a hilltop which he named Collurania (Urania Hill). He equipped his observatory with a fine 15.5-inch (39-cm) Cooke refractor, the largest instrument in Italy after the 19-inch (49-cm) refractor of the Brera Observatory in Milan. Like Flammarion's observatory at Juvisy and Lowell's at Flagstaff, the Collurania Observatory was a temple to the sky which owed its existence primarily to its founder's fascination with the planet Mars.
The turning point in Cerulli's study of Mars came on January 4, 1897, when there were "some moments of perfect definition [in which] Mars appeared perfectly free from undulation." Under these conditions, Cerulli watched with astonishment as the canal Lethes "lost its form of a line and altered itself into a complex and indecipherable system of minute patches."37 Though he had previously recorded, and indeed would continue to record, numerous canals, not only in the light areas but in the dark areas as well, Cerulli henceforth regarded the whole network with suspicion and published a book on the subject, Marte nel 1896--97. These observations were especially significant because Schiaparelli looked to Cerulli as his most promising successor, confiding to Otto Struve: "I had once hoped that such work might be done by Mr. Percival Lowell, but he is gravely ill; moreover he is more a literary man than an astronomer, much attracted to theatrical matters and sensational news. Signor Cerulli at Teramo is a man to be taken more seriously, and may yet do something solid, if only he resists the tendency he has shown to judge the observations by the theories in his head."38
Needless to say, Schiaparelli did not share Cerulli's interpretation of the canals.
Lowell, seized with a new intensity following his return to his observatory after his illness, spent the opposition years of 1901 and 1903 making extensive visual observations, despite the fact that Mars's distance from the Earth made these unfavorable opportunities. Among other things, he plotted the visibility of the canals as a function of Martian dates and latitudes to produce diagrams that he called "cartouches." The cartouches showed that both the canals and the dark areas participated in what he referred to as a "wave of darkening." Every spring and summer, this wave swept across the dark areas toward the equator. "Quickened by the water let loose on the melting of the polar cap," he wrote, the dark areas
|rise rapidly to prominence, to stay so for some months, and then slowly proceed to die out again. Each in turn is thus affected. . . . One after another each zone in order is reached and traversed, till even the equator is crossed, and the advance invades the territory of the other side. Following in its steps, afar, comes the slower wane. But already, from the other cap, has started an impulse of like character that sweeps reversely back again, travelling northward as the first went south. Twice each Martian year is the main body of the planet traversed by these waves of vegetal awakening, grandly oblivious to everything but their own advance.39|
Apart from the wave of darkening, Lowell noted changes in color that also seemed to be seasonal in nature and lent still further support to the vegetation theory. In 1903 he found that the Mare Erythraeum had turned from blue-green to chocolate brown as Martian autumn gave way to winter, then gradually began to become green again as Martian spring approached. On observing the same changes again two years later, he wrote: "Unlike the ochre of the light regions generally, which suggest desert pure and simple, the chocolate-brown precisely mimicked the complexion of fallow ground. When we consider the vegetal-like blue-green that it replaced, and remember further the time of year at which it occurred in both these Martian years, we can hardly resist the conclusion that it was something very like fallow field that was there uncovered to our view."40
Lowell was joined in his campaign to prove that there was life on Mars by his assistants V. M. Slipher and Lampland. In 1903, Slipher began spectrographic observations of Mars in an attempt to refute Campbell's negative observations and demonstrate the presence of water vapor there. Unable to obtain plates sensitive to the red part of the spectrum where the water vapor lines are found, he was forced, at least temporarily, to admit defeat. Lampland's project was photography of the planet, and in 1905 Lowell announced that his assistant had succeeded in photographing some of the canals, an achievement for which he was awarded the medal of the Royal Photographic Society. Schiaparelli wrote to Lowell, "I should never have believed it possible."41
Based mainly on his observations of 1903, though supplemented with results from the 1905 opposition, which he also observed extensively, Lowell wrote Mars and Its Canals, his magnum opus on the red planet. The book appeared in December 1906, at a time when public interest was intense. In addition to providing a massive résumé of Lowell's visual studies of the planet and his controversial interpretations, the book makes brief mention of Lampland's photographs, noting that "thus did the canals at last speak for their own reality themselves."42 Unfortunately, Lowell was unable to find a way to adequately reproduce Lampland's tiny, delicate images, each only a quarter inch (6 mm) across, and none of the photographs appear in the book. Among the various experts who examined the original images, some agreed that they showed the canals, but others were not so sure. Inevitably someone pointed out that even though there might appear to be linear details in the photographs, it did not follow that this was the actual form of the features on the planet's surface.43
The most notable response to the publication of Mars and Its Canals came from Alfred Russel Wallace, the octogenarian naturalist who as a young man had been co-discoverer (with Charles Darwin) of the theory of evolution by natural selection. Asked to review Lowell's book, Wallace, who regarded Lowell's book as "a challenge, not so much to astronomers as to the educated world at large," responded with a remarkable book of his own, Is Mars Habitable? In it he launched a devastating critique, not of Lowell's observations, which he accepted, but of Lowell's conclusions from them.44 Lowell had argued in a paper published in 1907 that the temperature on Mars was "comfortable as the south of England."45 Wallace effectively impeached Lowell's estimate of the albedo (reflectivity) of the Earth, which had been crucial to his reasoning.46 Instead of comfortable warmth, Wallace surmised, the temperature almost everywhere on Mars was probably very far below the freezing point of water. If so, the polar caps might well be frozen carbon dioxide, as had been proposed some years earlier by A. Cowper Ranyard and G. Johnstone Stoney, rather than water ice. As for Lowell's idea of water-filled canals, Wallace wrote scathingly: "Any attempt to make that scanty surplus, by means of overflowing canals, travel across the equator into the opposite hemisphere, through such terrible desert regions and exposed to such a cloudless sky as Mr. Lowell describes, would be the work of a body of madmen rather than of intelligent beings. It may be safely asserted that not one drop of water would escape evaporation or insoak at even a hundred miles from its source."47
Despite Wallace's book, however, the public continued to support Lowell and his theory of life on Mars. His secretary, Wrexie Leonard, described the frenzied response to his 1906 lecture series for the Lowell Institute at Boston's thousand-seat Huntington Hall: "Standing room was nil, and demands for admission were so numerous and insistent that repetitions were arranged for the evenings. At these repeated lectures the streets near by were filled with motors and carriages as if it were grand opera night!"48
Lowell remained very much in the public eye at the opposition of 1907, when Mars was near the Earth but too far south to be studied satisfactorily from northern observatories. While he remained in Flagstaff to observe the planet visually with the 24-inch refractor, his assistant E. C. Slipher went with Amherst College professor David Peck Todd to Alianza, Chile, in order to photograph the planet with Amherst's 18-inch (46-cm) refractor, which had been shipped to South America specifically for that purpose. The telescope was set up in the open desert with only the sky for a dome, and some of Slipher's 13,000 images were alleged to have captured canals---including, Slipher announced, some of the more prominent doubles. Naturally, Lowell was excited by this apparent success, and he wrote to Todd: "Bravo! . . . The world, to judge from the English and American papers, is on the qui vive about the expedition, as well as about Mars. They send me cables at their own extravagant expense and mention vague but huge (or they won't get 'em) sums for exclusive magazine publication of the photographs."49 Eventually the bidding war for publication rights was won by Century magazine, but as before, the delicate detail of the photographs proved difficult to reproduce satisfactorily, and the photographic evidence of the canals remained inconclusive.
All of this controversy only served to pique interest in the next opposition, in 1909. Mars would be only slightly closer to the Earth than it had been in 1907, but it would be far better placed for northern observatories. More large telescopes would be trained on it than at any other time in history, thus setting the stage for what would prove to be the dramatic climax to the long and heated debate over the Martian canals.
© 1996 The Arizona Board of Regents