When, returning from Japan late in 1893, Percival Lowell found himself quickly absorbed by astronomical research, he was by no means without immediate equipment for the task. His mathematical capacity, that in college had so impressed Professor Benjamin Peirce, had not been allowed to rust away; for, when at home, he had kept it bright in the Mathematical and Physical (commonly called the M. P.) Club, a group of men interested in the subject, mainly from Harvard University and the Massachusetts Institute of Technology. So fresh was it that we find him using, at the outset, with apparent ease his calculus—both differential and integral—tools that have a habit of losing edge with disuse. Physically, also, he had a qualification of great importance for the special work he was to undertake,—that of perceiving on the disks of the planets, very fine markings close to the limit of visibility; for the late Dr. Hasket Derby, then the leading practitioner in Ophthalmology in Boston, told Professor Julian Coolidge that Percival’s eyesight was the keenest he had ever examined.
One essential remained, to find the best atmosphere for his purpose. In entering our air the rays of light from the stars are deflected, that is bent, and bent again when they strike a denser or less dense stratum. But these strata are continually changing with currents of warmer or colder air rising and falling above the surface of the earth, and hence the rays of light are being shifted a little from side to side as they reach us. Everyone is familiar with the twinkling of the stars, caused in this way; for before entering our atmosphere their light is perfectly steady. Moreover, everyone must have observed that the amount of twinkling varies greatly. At times it is unusually intense, and at others the stars seem wonderfully still. Now, although the planets, being near enough to show a disk visible through a telescope, do not seem to twinkle, the same thing in fact occurs. The light is deflected, and the shaking makes it very difficult to see the smaller markings. Imagine trying to make out the detail on an elaborately decorated plate held up by a man with a palsied hand. The plate would be seen easily, but for the detail one would wish it held in a steadier grasp, and for observing the planets this corresponds to a steadier atmosphere.
Percival’s own account of the reason for his expedition of 1894 to observe the planet Mars, why he selected Flagstaff as the site, what he did there and how the plan developed into the permanent observatory that bears his name were told in what was intended to be an introduction to the first volume of the Annals of the Observatory. Perhaps owing to the author’s illness in the last years of the century this statement was mislaid and was not found until February 22, 1901. It is here printed in full.
Annals of the Lowell Observatory
INTRODUCTION
In the summer of 1877 occurred an event which was to mark a new departure in astronomy,—the detection by Schiaparelli of the so-called canals of the planet Mars. The detection of these markings has led to the turning over of an entirely new page in cosmogony.
Schiaparelli’s discovery shared the fate of all important astronomical advances,—even Newton’s theory of gravitation was duly combatted in its day,—it, and still more the possibilities with which it was fraught, distanced the comprehension of its time. In consequence, partly from general disbelief, partly from special difficulty, no notable addition was made to Schiaparelli’s own work until 1892, when Professor W. H. Pickering attacked the planet at the Boyden Station of the Harvard Observatory at Arequipa, Peru, and made the next addition to our knowledge of our neighbor world.
Intrinsically important as was Pickering’s work, it was even more important extrinsically. Schiaparelli’s discoveries were due solely to the genius of the man,—his insight, not his eyesight, for at the telescope eyes differ surprisingly little, brains surprisingly much; Pickering’s brought into coÖperation a practically new instrument, the air itself. For at the same time with his specific advance came a general one,—the realization of the supreme importance of atmosphere in astronomical research. To the Harvard Observatory is due the first really far-reaching move in this direction, and to Professor W. H. Pickering of that observatory the first fruits in carrying it out.
It was at this stage in our knowledge of the possibilities in planetary work and of the means to that end, in the winter of 1893-94, that the writer determined to make an expedition which included the putting up of an observatory for the primary purpose of studying, under the best procurable conditions, the planet Mars at his then coming opposition,—an opposition at which the planet, though not quite so close to us as in 1892, would be better placed for northern observers. In this expedition he associated with himself Prof. W. H. Pickering and Mr. A. E. Douglass.
The writer had two objects in view:
1st, the determination of the physical condition of the planets of our solar system, primarily Mars;
2d, the determination of the conditions conducive to the best astronomical observations.
How vital was the inter-connection of the two was demonstrated by the results.
Important as atmosphere is to any astronomical investigation, it is all-important to the study of the planets. To get, therefore, within the limits of the United States—limits at the time for several reasons advisable—as steady air as possible, Prof. W. H. Pickering, who had already had experience of Southern California as well as of Arequipa, Peru, proposed Arizona as the most promising spot. Accordingly, Mr. A. E. Douglass left Boston in March, 1894, with a six-inch Clark refractor belonging to the writer, to make a test of the seeing throughout the Territory. From his report, Flagstaff was selected for the observatory site.
Flagstaff, then a town of eight hundred inhabitants, lies on the line of the Atlantic and Pacific Railroad, in the centre of the great plateau of northern Arizona, half way across the Territory from east to west, and two fifths way down from north to south. This plateau, whose mean elevation is between 6000 and 7000 feet, is a great pine oasis a hundred miles or more in diameter, rising some 3000 feet from out the Arizona desert. It culminates in the mass known as the San Francisco Peaks, ten miles north of Flagstaff, whose highest summit rises 12,872 feet above the level of the sea.[9]
The spot chosen was the eastern edge of the mesa (table-land) to the west of Flagstaff. The site lay open to the east and south, and was shielded on the north by the San Francisco Peaks. The distance from the observatory to Mt. Agassiz, the most conspicuous of the Peaks from the Flagstaff side, was about eight miles and three fifths in an air-line, and the distance to the town about a mile and a quarter. As soon as the site was selected, the town very kindly deeded to the observatory a piece of land and built a road up to it.
The observatory stood 350 feet above the town, and 7250 feet above the level of the sea, in latitude 35° 11' north and longitude 111° 40' west.
Prof. W. H. Pickering, to whose skill and ability was chiefly due the successful setting up of the observatory, suggested arrangements with Brashear for the use of an eighteen-inch refractor which Brashear had recently constructed,—the largest glass to be had at the time,—arrangements which were accordingly made. He then devised and superintended the construction of a dome intended to be of a temporary character, which worked admirably. The upper part of it was made in sections in Cambridgeport, Mass., and then shipped West, the lower part being constructed according to his specifications on the spot, under the superintendence of Mr. Douglass.
The telescope was supported on one of the Clark mountings. The bed-plate, clock-work, and a twelve-inch telescope were leased of the Harvard College Observatory, and the mounting then altered by Alvan Clark & Sons to carry both the twelve and the eighteen-inch telescopes.
Six weeks from the time ground was broken, on April 23, 1894, regular observations with the eighteen-inch were begun.
The results of the year’s work surpassed anticipation. Details invisible at the average observatory were presented at times with copper-plate distinctness, and, what is as vital, the markings were seen hour after hour, day after day, month after month. First sight; then system; and the one of these factors was as fundamental to the results as the other. Systematic work, first made possible and then properly performed, was the open sesame to that most difficult branch of astronomical observations, the study of our nearest neighbors in the universe.
The chief results obtained were:—
1st, the detection of the physical characteristics of the planet Mars to a degree of completeness sufficient to permit of the forming of a general theory of its condition, revealing beyond reasonable doubt first its general habitability, and second its particular habitation at the present moment by some form of local intelligence;
2d, corroboration and extension by Professor Pickering of his discoveries at Arequipa with regard to the forms of Jupiter’s Satellites;[10]
3d, the discovery and study by Mr. Douglass of the atmospheric causes upon which good seeing depends.
It is of the observations connected with the first of these that the present volume of the Annals alone treats.
As the publication of this volume has been so long delayed, it seems fitting to add here a brief continuation of the history of the observatory to the present time.
The results of the expedition in 1894, in the detection of planetary detail, turned out to be so important an advance upon what had previously been accomplished that the writer decided to form of the temporary expedition a permanent observatory. Accordingly, he had Alvan Clark & Sons make him a twenty-four-inch refractor, which fate decided should be their last large glass; the Yerkes glass, although not yet in operation at the time this goes to press, having been finished at nearly the time his was begun. The glass received from Mantois happened to be singularly flawless and its working the same. It was made twenty-four inches in clear aperture, and of a focal length of thirty-one feet. Alvan G. Clark accompanied the writer to Flagstaff and put the glass in place himself.
The mounting for the telescope was likewise made by the Clarks. Rigidity was the prime essential, in order to secure as stable an image as possible, and this has been admirably carried out, the mounting being the heaviest and most stable for a glass of its size yet made.
In July, 1896, Dr. T. J. J. See joined the observatory, to continue there the line of research for which he was already well known—the study of the double stars. This added to the two initial objects of the observatory a third,—
3d, the study of double-star systems, including a complete catalogue of those in the southern heavens.
During the summer and autumn of 1896 the importance of good atmosphere was further demonstrated in an interesting and somewhat surprising quarter. The air by day was found to be as practicable as that by night. While Mars was being studied by night, the study of Venus and Mercury was taken up during the daytime systematically, and the results proved as significant as had been those on Mars. Instead of the vague diffused patches hitherto commonly recorded, both planets’ surfaces turned out to be diversified by markings of so distinct a character as not only to disclose their rotation periods but to furnish the fundamental facts of the physical conditions of their surfaces. We know now more about Mercury and Venus than we previously knew of Mars.
As the winter in Flagstaff is not so good as the summer, it was thought well to try Mexico during that season of the year. Accordingly, a new dome was made; the telescope was taken down; and dome, mounting, and glasses were carried to Mexico and set up for the winter at Tacubaya, a suburb of the City of Mexico, at an elevation of 7500 feet. There the observatory received every kindness at the hands of the President, the Government, and the National Observatory.
Observations at Mexico fully corroborated those at Flagstaff with regard to both Mars, Mercury and Venus, and enabled Mr. Douglass to make the first full determination of the markings on Jupiter’s third and fourth satellites, thus fixing their rotation periods.
Dr. See in the mean time, who while at Flagstaff had discovered a very large number of new doubles, in Mexico added to his list;...
With the spring the observatory was shipped back again to Flagstaff.
Of the particular results in planetary work obtained, several papers have been published in various astronomical journals, while of them subsequent volumes of the Annals will speak in detail. In the meantime two general conclusions to which they have led the writer may, as possessing future interest, fittingly be mentioned here:
1st, that the physical condition of the various members of our solar system appears to be such as evolution from a primal nebula would demand;
2d, that what we call life is an inevitable detail of cosmic evolution, as inherent a property of matter from an eventual standpoint as gravitation itself is from an instant one: as a primal nebula or meteoric swarm, actuated by purely natural laws, evolves a system of bodies, so each body under the same laws, conditioned only by size and position, inevitably evolves upon itself organic forms.
The reasons for the first of these conclusions have sprung directly from the writer’s study of the several members of our own solar system; his reason for the second, upon the further facts,—
1st, that where the physical conditions upon these bodies point to the apparent possibility of life, we find apparent signs of life;
2d, where they do not, we find none.
This implies that, however much its detail may vary, life is essentially the same everywhere, since we can reason apparently correctly as to its presence or absence, a result which is in striking accord with the spectroscopic evidence of a practical identity of material.
Evidently the expedition to observe Mars was undertaken quite suddenly, but if it was to be made at all it must be done quickly. Anyone, however unfamiliar with astronomy, will perceive that two planets revolving about the sun in independent orbits will be nearest together when they are on the same side of the sun and farthest apart when on opposite sides of it, and that the difference is especially great if, as in the case of the earth and Mars, their orbits are not far apart, for when on the same side the separation is only the difference of their distances from the sun, and when on opposite sides it is the sum of those distances. Moreover, Mars being outside of the Earth its whole face is seen in the full light of the sun when both bodies are on the same side of it. Now such a condition, called opposition, was to occur in the summer after Percival’s return from Japan, and therefore there was no time to spare in getting an observatory ready for use.
From the experience of others elsewhere, Percival was convinced that the most favorable atmospheric situations would lie in one of the two desert bands that encircle a great part of the Earth, north and south of the equator, caused by the sucking up of moisture by the trade winds; and that a mountain, with the currents of air running up and down it, did not offer so steady an atmosphere as a high table-land. The height is important because the amount of atmosphere through which the light travels is much less than at sea level. He was aware that the best position of this kind might well be found in some foreign country; but again there was no time to search for it, or indeed to build an observatory far away, if it must be equipped by the early summer. The fairly dry and high plateau of northern Arizona seemed, therefore, to offer the best chance of a favorable site for this immediate and temporary expedition.
With the aid of suggestions by Professor William H. Pickering, who knew what was needed in observing Mars, he sent Mr. Douglass, with the six-inch telescope brought back from Japan, to Arizona to inspect the astronomic steadiness of the atmosphere. The instructions, apparently drawn up by Professor Pickering, were dated February 28th, directing him to observe on two nights each at Tombstone, Tucson and Phoenix; and Percival, keeping in constant touch with Mr. Douglass by letter and telegraph, added among other places Flagstaff. This was shortly followed by instructions about constructing the circular vertical part of the dome for the observatory by local contract as soon as the site was selected, while the spherical part above, which was to be of parallel arches covered with wire netting and canvas, was being made in the East and to be shipped shortly. Meanwhile the pier was being built by Alvan Clark & Sons (who had made most of the large telescopes in this country) and the mounting for both the eighteen-inch and the twelve-inch telescope thereon, balancing each other. Mr. Douglass was to report constantly; and in April Percival wrote him to take a photograph of the site of the observatory “now,” then every day as the work progressed, and have the negatives developed, a blue print made of each as speedily as possible and sent East. All this is stated here to show the speed, and at the same time the careful thought, with which the work was done. Percival and his colleagues came as near as possible to carrying out the principle, “when you have made up your mind that a thing must be done, and done quickly, do it yesterday.”
In fact Percival did not select any of the three places first examined, but on consideration of Mr. Douglass’ reports preferred Flagstaff; and his choice has been abundantly confirmed by the pioneering problems undertaken there, and by the fact that this site was retained for the later permanent Observatory. Everyone, indeed, deserves much credit for the rapid work done at such a distance from principals busy with the preparation of the instruments. It was characteristic of Percival that he got the very best out of those who worked with and under him.
Although the closest point of the opposition did not occur until the autumn, the two planets, travelling in the same direction, were near enough together for fair observation some months earlier; and on May 28th, arriving at Flagstaff, Percival writes to his mother: “Here on the day. Telescope ready for use tonight for its Arizonian virgin view.... After lunch all to the observatory where carpenters were giving their finishing touches.... Today has been cloudy but now shows signs of a beautiful night and so, not to bed, but to post and then to gaze.” The sky was not clear that night, for an unprecedented rain came and lasted several days, falling through the still uncanvased dome on Professor Pickering and Percival, who had been lured by a “fairing” sky into camping out there in the evening to be on time for the early rising Mars. But it was not long before the weather cleared and the strenuous work began. As the observatory was a mile and a half from the hotel in the town, and uphill, it was uncomfortable to arrive there at three o’clock in the morning, the hour when at that season Mars came in sight. So in the summer a cottage was built hard by the dome, where they could sleep and get their meals.
The observations were, of course, continuous throughout the rest of the year; and except for two trips East on business, one for a few weeks at the end of June, another in September, and a few days in Los Angeles, Percival was there all the time. As usual he worked furiously; for beside observing most of the night he spent much of the day writing reports and papers, making drawings for publication in scientific and other periodicals, and investigating collateral questions that bore upon their significance; and while he had computers for mechanical detail, he and his colleagues had to prepare and supervise their work. To his mother he wrote, as a rule, every day; and in some of these letters he gave an account of his time. On September 2nd, he writes of being up the greater part of the night, and naturally perpetually sleepy. “But the number of canals increases encouragingly—in the Lake of the Sun region we have seen nearly all Schiaparelli’s and about as many more.” On October 10th: “Observed the better part of last night, after being welcomed by everybody—and have been as a busy as a beaver today, writing an article, drawing for ditto etc, etc.”; and, two days later, “Chock full of work; scrabbling each day for the post—proof etc. Mr. Douglass is now on the hill observing Mercury. We all dine there at seven. Then I take Mars and at 3 A.M. Professor Pickering, Jupiter. So you see none of the planets are neglected.”
In one of these letters he encloses a clipping from a San Francisco newspaper satirizing Professor Holden for saying that the canals of Mars reported at Flagstaff were not confirmed by observations at Mount Hamilton. Denial or doubt that he had really seen what—after many observations confirmed by those of his colleagues—he reported as seen always vexed Percival, and naturally so. Yet they were not uncommon and sometimes attributed to defective vision. He was well aware that while a belief that a thing exists may make one think he has seen it when he has not, yet it is also true that one person perfectly familiar with an object sought will find it when another, unacquainted with its precise appearance, will miss it altogether. Everyone knows that people in the habit of looking for four-leaved clovers are constantly picking them while others never see them; or that a skilled archaeologist finds arrowheads with much greater facility than a tyro, who will, however, improve rapidly with a little experience; and all this is especially true of things near the very limit of visibility. Gradually more and more observers began to see the finer markings and the canals on Mars, until finally the question of their existence was set at rest when it became possible to photograph them.
But in spite of work and vexation the life was far from dull, for the observatory was as hospitable as its limited quarters would allow. Visitors were attracted by its growing reputation, and on August 25th he writes: “Just as we were plodding up there last evening in the dark we heard a carriage-full of folk coming down. We suspected what they had been after and were not surprised when they challenged us with ‘Are you observatory people?’ It seems they were, as they informed us pathetically, people from the East and had gone up to look through the glass, if they might, before taking the train at 12.30 that night. Of course we could not resist their appeals and so, though we had thought to turn in betimes because of early observations in the morning, entertained these angels—half of them were women—on ‘just like diamonds’ as they said of the stars. The out-of-focus views pleased them the most—as turns out to be the case generally. This morning when I went to take Pickering’s place I found another angel in the shape of a Colorado man, out here for his health, in the dome with Pickering—a nice fellow he turned out. It was then 4 h. 8 m. o’clock in the morning,—a matutinal hour for a man to trudge a mile and a half on no breakfast up to an observatory on a hill—That shows real astronomical interest. He was rewarded gastronomically with some coffee of my brewing, all three of us breakfasting standing by the platform.”
There were occasional picnics and trips to the cave dwellings, the Grand CaÑon, the petrified forest and other sights. Moreover, Percival greatly enjoyed the scenery about Flagstaff, and took an interest in the people of the town, although well aware of inexperience in some matters. On October 13th he says: “There was a grand republican rally last night and the young Flagstaff band that is learning to play in tune serenaded the speaker of the occasion under the hotel windows in fine style. When you knew the air beforehand you could follow it with enthusiasm.”
