Popular Science Monthly/Volume 68/June 1906/An Eclipse Expedition to Spain
|AN ECLIPSE EXPEDITION TO SPAIN|
By Dr. S. A. MITCHELL
IF we could sum up the total duration in minutes and seconds of recent eclipses, we should be astounded that astronomers from such phenomena have discovered so very much. Since the spectrograph and the photographic plate were first used together at an eclipse, the sun has been covered up by the moon somewhat less than twenty minutes of time, yet, in these few moments, a great wealth of information has been gained from the eclipsed spectrum. Each eclipse settles some problems, and teaches us how to attack others, and astronomers are most enthusiastic at such a time, trying new instruments and improved methods of research. More interest was shown in the 1905 eclipse than ever before, one reason for this being that the moon's shadow path fell upon a readily accessible part of the globe, and the eclipse occurred at a time of the year (August 30) when most college men were having their summer vacation. At the last eclipse, in 1901, American astronomers had to travel as far away from home as possible, in that a trip half way round the world was taken; and when one considers the number of instruments, and the great amount of freight that the modern astronomer has to carry with him, the task is no small one.
At the eclipse of last year the moon's shadow touched the earth's surface at sunrise in Manitoba, and after crossing through Canada at cannon-ball speed, it left Labrador about 8 a. m. on its trip across the Atlantic. Shortly after noon the shadow cut into Spain, then on through the Mediterranean, northern Africa, Egypt, and left the earth's surface at sunset on the coast of the Indian Ocean.
Spain was chosen by the majority of astronomers, both because the duration of totality was longer, and because the weather conditions promised better; and here in a path one hundred and twenty miles in width running diagonally across the peninsula, hundreds of astronomers, American and European, were gathered.
The party sent out by the United States government was under the general direction of Rear-Admiral Colby M. Chester, U.S.N., superintendent of the Naval Observatory. Three men-of-war were furnished by the Navy Department for the purposes of the expedition, the U.S.S. Minneapolis, U.S.S. Dixie and U.S.S. Cæsar, the first named being the flagship of the squadron.
The three vessels left separately from the United States about the end of June, and met in Gibraltar about the middle of July. 'Gib' is one of the most interesting places in the world, especially when entering on a naval vessel. It was a glorious sight, as we steamed in at dawn, to behold the wonderful rock, and sheltered at its base the Mediterranean squadron of the British navy, consisting of eight battleships and eight first-class cruisers, under the greatest of English admirals, Lord Charles Beresford. The morning of our arrival was spent in firing and acknowledging thunderous salutes, and in making official calls. To properly carry out these acts of courtesy between the American and British nations, it was necessary to fire no less than one hundred and fifty-two rounds of ammunition. On the morning of our second day in Gibraltar, the British squadron sailed, and it gave us an
U. S. S. Minneapolis, entering Valencia Harbor.
idea of the quality of the greatest navy in the world to see the splendid, seamanlike manner in which the big ships got under way, and without confusion, and in splendid order one by one depart from the crowded harbor.
Gibraltar covers only about two square miles, so it did not take much time for us to take in all the sights of the streets with their motley population of English, Spanish and Moors, and to visit the places of historical interest. The 'Key of the Mediterranean' stretches almost exactly from north to south with a length of three miles and a breadth of little more than half a mile. The north and east sides of the 'rock' are almost vertical, while to the south and west it descends in step-like terraces, and thus it is only a small portion of the area of two square miles that is habitable. From the foot of Mt. Rockgun (1,356 feet) the land stretches northward towards Spain in a low-lying flat isthmus not more than half a mile in width. The central portion of this, a third of a mile in width, is kept as a neutral zone between the Spanish and British possessions, and is lined with sentry boxes on either side. The fortifications of the side towards Spain consist mainly in galleries hollowed out in the face of Rockgun during the four years' siege ending in 1783. Signal Station (1,295 feet) and Highest Point (1,396 feet) are surmounted with great guns which defend the twelve miles of strait that flow between Europa point and Africa.
Entering the blue waters of the Mediterranean, the Minneapolis steamed along the coast of Spain for about four hundred miles and
anchored in the harbor of Valencia, the first American man-of-war to visit a Spanish port since the late unpleasantness.
At Valencia, the home of the 'Cid,' the annual fair was in progress, and the chief attraction was the bull fight. During the eight days of the fair, five Corridas de toros were held. Six bulls were killed at each of four of these fights, and in the other, 'extra-special' fight, eight bulls were slaughtered. Those of us who went to the first of these disgusting spectacles saw six bulls and nineteen horses butchered, and it is hardly necessary to remark that we did not go a second time.
The bull ring is of the shape that the name signifies, the one in Valencia being the largest in Spain, capable of holding 17,000 people. The fight is opened by a procession into the ring of those taking part. At the head of the procession walk the Espadas, then come the Banderilleros, the mounted Picadores and the attendants (Chulos) on foot with a team of gaily bedecked mules used in dragging off the dead bulls and horses. The fight can be described as follows:
It is one of three acts. In the first act the picadores receive the charge of the bull, which they try to withstand by prodding him with their pikes. In nearly every case horse and rider are overthrown by the bull, and the horse terribly gored. The bull's attention is attracted as quickly as possible by the waving of cloaks in the hands of attendants, and he is enticed to leave the prostrate man and horse. This, performance is repeated several times until the bull becomes a little wearied. The second act now begins, and in this a banderillero on foot will meet the bull in full charge, stick into his neck on either side two barbed darts about thirty inches long covered with colored paper, and step nimbly aside to escape the enraged animal. Usually eight of these darts are used. In the third and last act, the espada teases the bull with his red cloth and manœuvers to get the weakened bull in a favorable position to give the death stroke by thrusting his sword through the neck and into the bull's heart. Great is the applause when the bull falls dead from a single stroke. The dead bull and horses are dragged out by the mule team, the ring is sanded to cover up all traces of blood, a new bull is let in and the fight goes on as before. (A bull fight is quite expensive. Each bull costs about $250, and horses, though poor, cost something. The animals killed in the ordinary corrida are worth at least $2,000.)
It had been decided to divide the Naval Observatory expedition into three, sending two parties to Spain and one to Africa. The U. S. S. Dixie took the African party to Tunis, and the astronomers Jewell, Gilbert and Dinwiddie located themselves at Guelma near the central line of the shadow cast by the moon. In Spain there were two parties, one located at the edge of the path of totality at Poerto Coeli, and the other near the central line at Daroca. At the former place were Lieutenant Commander Hayden, Professor Littell, Mr. Peters and Mr. Hill from the Naval Observatory, and Mr. Anderson from the Johns Hopkins University; at the latter place were stationed Professor Eichelberger and Mr. Yowell of the U. S. Naval Observatory, Professor Bigelow of the U. S. Weather Bureau, Mr. Hoxton of the Johns Hopkins University, and the writer.Daroca is in the heart of old Spain, about forty miles from Saragosso, and as a railroad has been there only four years it is a terra incognita for modern tourists—for which we were duly thankful. Our six weeks' stay there was a happy commingling of hard work—and there was plenty of work to do—with pleasant experiences in getting acquainted with Spanish life and people. The site for the town is indeed a peculiar one, in a valley so surrounded by hills that each
heavy rain storm used to flood the city till, about 1600, a tunnel was constructed through one of the hills to carry away the waters. The tops of these hills are crowned with walls and forts, most of them constructed by the Moors a thousand years ago, some of them by the
Catholic Spanish since that time. There is one tower of special interest, and still in good state of preservation, which is said to have been built by the Romans before Saguntum was founded, and it is, therefore, more than two thousand years old. (The railroad from Valencia passes through Saguntum where Hannibal and the Romans had their memorable fight in B.C. 238.)
The Spaniards received us with open arms and did everything in their power to assist in our work and to make our stay in their midst as pleasant as possible. As no one in the place could speak English, it was necessary to make ourselves understood in their language. They did not laugh at our mistakes in grammar or pronunciation, as we might have done in their places, but were always and at all times the souls of politeness and courtesy.
To help in the erection of the observatory, six sailors were sent in from the Minneapolis, and all hands, astronomers and sailors, worked each day from early morning till late at night, building piers, erecting telescopes with houses to shelter them, mounting spectroscopes, and fixing up a meteorological observatory. After the carpenters and machinists had finished their work of construction, it was necessary for the scientists to focus and adjust, to see that everything was in good working order, and to make trial photographs. A few days before the eclipse the party increased in size to thirty-five, officers and sailors having come up from the ship for the purpose of assisting in the observations. Frequent drills were held in order to familiarize each one with his part and thus to be sure that everything would go right and that no precious seconds would be wasted at the time of the eclipse.
There are certain things about the sun of which we still know very little: for instance, our information of the corona does not go very far. This wonderful halo, without doubt the most beautiful of all natural phenomena, can be seen only when the sun's light is totally eclipsed. As long as there is a slight trace of the sun's disc to be seen, its light is so overpowering that the corona is obliterated; but the instant the moon completely covers it up, there flashes out instantaneously the gorgeous crown of light to view which is well worth traveling thousands of miles. At this eclipse the corona lasted for three minutes and forty-five seconds, and almost with the first reappearance of the sun it was gone. Although this crown must be at all times around the sun, astronomers have not yet become expert enough to make it visible without an eclipse. The shape of the corona, too, is peculiar in that it is in some manner connected with the number of spots on the sun. When there are very few spots, the corona is winged out on either side along the sun's equator, while in the years that the spots are many, the streamers run out at all angles and the corona is more or less square in shape. We have known for more than fifty years that there is some close bond between the number of spots and the amount of magnetism in the earth. This terrestrial magnetism is evidenced through changes in the compass needle, in frequent magnetic 'storms' and in the beautiful northern lights. The sun spots are thus the seat of some great solar activity of whose exact nature we are at present not sure. Moreover, the sun is not sending to the earth a constant amount of heat. Very recent observations in Washington show that these solar fluctuations are followed very closely by variations in temperatures all over the earth. Whether these newly discovered variations in the sun's heat are connected with the spots on the sun, or not, it is too early to say, but it may not be outside the bounds of possibility to be able in the future to forecast the great variations in our earthly temperatures from observations on the sun. We realize, then, the importance of
these observations on the sun, and it is for the solution of problems such as these that eclipse expeditions are sent out.
To investigate the corona, photographs are taken of all sizes. The diameter of the sun on the photograph depends on the length of the camera, the greater the focus the larger the sun. At Daroca the largest camera used was forty feet in length, which gave an image of the sun four inches in diameter. In photographing, the lens can be mounted pointing directly at the sky, or else the whole instrument can be placed horizontally and light be reflected into it by means of a mirror. We adopted the latter way as being the easier.
The location of the eclipse camp was half a mile south of the town, in the midst of a beautiful, fertile valley. From there, while we worked, we could catch glimpses of scenery typical of Spain. The first feature to attract your attention is the extremely barren aspect of the country, which is in sharp contrast with the garden-like appearance of England. The hills of Spain were in early times densely wooded, but now are almost entirely devoid of trees and look from a distance as if there were not a particle of vegetation on them. Moreover, the rainfall is so slight that agricultural pursuits must rely upon irrigation for their carrying on, and thus it is only the valleys that are green and cultivated. In such a valley along the shores of the little river was our eclipse camp located. The greenest field was decided upon as the site of the observatory, and upon application to its owner for permission we found that he was quite satisfied to allow his plot of ground to be used, but thought some compensation should be made for the valuable crop of grass that might possibly be raised during the summer. On receipt of one hundred pesetas, he forthwith proceeded to take a fatherly interest in all of our doings, and explained scientific matters to every one as if he had been chief of the expedition. His field became the center of interest in the community, and people came from all sides to look upon the strange doings. As a prominent trait in the Spanish make-up is a great and overpowering curiosity, we had plenty of onlookers; and when the mayor and a few of the most prominent citizens were invited to look at the moon through our five-inch telescope, we were rather surprised—to put it mildly—to find over one hundred people turn up, when only a half score had been invited. Their curiosity took the form only of making each and every one in the town intensely interested in what was going on, and to show that interest they turned out in force each afternoon to see how matters were progressing. It might be asked, what was their attitude towards these Americans who had so lately beaten them in their small war. Before the expeditions reached Spain, it was feared that perhaps there might be some friction on that account, but these fears were not realized. As a matter of fact, the only person we met who seemed to have any feeling in the matter was a former soldier in the Spanish army. He had seen service in the Philippines, had been captured and thrust into prison by the Filipinos, had been rescued by the Americans, and as a result he had only the kindest of feelings towards everything belonging to the United States. As for the rest of the people, they seemed to have forgotten all about it, or else they did not know there had been a war, for it must not be forgotten that only about one quarter of the people in Spain can read and write.Besides getting photographs of the corona of different sizes, the astronomers at Daroca were using the most powerful spectroscopes ever employed at an eclipse, for the purpose of investigating the nature of the light of the sun and its surrounding region. There are two ways of producing a spectrum. The best known method is by means
of a triangular prism of glass which breaks up the white light of the sun into its component colors of red, orange, yellow, green, blue, indigo and violet. The other and better way is by the use of a grating. Such at. instrument is made by ruling on the surface of a plane or concave mirror many thousand tine lines separated by equidistant intervals. The writer had mounted for his use at the eclipse five spectroscopes, two being prisms, the others gratings. By means of these a great variety of problems were attacked, such as the constitution of the atmosphere immediately surrounding the sun and the heights in miles to which the different gases extend above the sun's surface, the nature of the gases that go to make up the beautiful corona, the amount of heat and energy of the corona, etc.
After this my third total eclipse, I can confidently say that observations at such a time consist of much hard work and many nerveracking experiences. One is never on hand sufficiently long beforehand to take things quietly and easily, you must work under conditions you are totally unused to, and over your head hangs the knowledge that everything must be completed by a certain day and a certain hour, for the eclipse can not be postponed, and there is no second trial in case of failure. In addition to working hard all day as carpenter and instrument maker, the astronomer must stay up half the night adjusting his instruments on stars, so that during the last few days before the eclipse very few hours of sleep each night are obtained. However, in spite of the many difficulties that were continually cropping up, the mounting and adjusting the instruments were practically completed by August 25, when our observing party was swelled in numbers by the officers and men from the Minneapolis. From then till eclipse day the time was spent in putting the finishing touches on the work of adjustment, and in having frequent drills in order to insure that everything would go without a hitch.
Eclipse was to occur shortly after noon on August 30, and for many days beforehand we had been carefully scrutinizing the weather in order to see what conditions we might possibly have to expect. As a rule the sky was clear at eclipse time. It would have been dreadfully disappointing to have had a cloudy day, or even to have a stray cloud cover the sun during the important few minutes of the total eclipse. Such a thing happened at the last eclipse in 1901 after traveling half way round the world. Where some of the observers were, the sky was so overcast that it was impossible even to see where the sun was. At the 1905 eclipse darkness lasted for the space of three minutes and forty-five seconds, and it was only during these few minutes, after weeks and months of preparation, that the real work was to be done. August 29 had been cloudy all day so that on eclipse day we had to go to camp early to test our final adjustments, go through drills once more and to be sure that all the apparatus worked smoothly. The skies were clear and our hopes for success were high. Outside the roped-off enclosure, the whole town of Daroca was assembled, for it was naturally thought that nowhere could the eclipse be seen so well as where the astronomers were located.
At 11.52 a. m. a little shadow was seen on the western limb of the sun, and the eclipse had begun. The skies were clear with the exception of a cloud here and there, and our most ardent wish was that the clouds would leave the sun clear for the next couple of hours. For the first hour that the moon was creeping over the sun there was nothing of very great moment to notice, but for the next twenty minutes till 1.12, when the sun was blotted out, we were each of us filled with expectancy, for matters began to take on a weird and unnatural appearance. The little blotches of light under the trees, instead of being the familiar circles, were little crescents, exact counterparts of the sun itself. The darkness began to make itself really felt, and without looking at the sun one would know that something out of the ordinary was happening, for the gloom did not in the slightest degree resemble that of sunset. A hush fell upon the crowd of assembled and talkative Spaniards when, ten minutes before totality, a big cloud drifted over the sun. Would this cloud move away? Or were we going to be disappointed? It hung there for a space of time that seemed to be an age, while in reality it was only five minutes. It was a big scare, but when
that passed, with a shout from us all, there wasn't another cloud anywhere to bother us. Fifteen seconds before the calculated time, with the last disappearing ray of sunlight, the corona broke forth into view. What a magnificent sight it is shining out with its pale, pearly light for a couple of diameters round the edge of the sun, with its streamers and brushes of delicate light! True to prediction, the corona was almost square in shape, and was not at all alike in appearance to the other coronas the writer had seen in 1900, and 1901, with their long fish-tail extensions along the sun's equator and short-curved steamers near the sun's poles. In the upper left-hand quadrant huge red flames sixty thousand miles high could be seen with the naked eye, which with a closer view with the telescope resolved themselves into a forest-like structure. These we know are great jets of burning hydrogen gas. Close to the sun the corona was very bright, in fact so bright that the eye was not readily able to take in all the details of the faint streamers. As a pictorial effect without the long equatorial extensions, this corona was much inferior to the two last ones seen. Still it was a magnificent sight, and we were more than thankful for having clear skies to make our observations.
When totality first started we were each and all of us much too busy to take much notice of our immediate surroundings or even the corona itself. We could not help becoming aware that our Spanish onlookers outside the ropes were appreciating the show in the skies provided for them without expense. From the noise made each one seemed to be telling his neighbor at the top of his voice just how it happened and what there was worth seeing, and this in spite of the fact that the mayor of Daroca had generously provided half a dozen members of the civil guard to preserve order and keep quiet. For the first half minute the din was so great that it was impossible to hear the seconds counted, or to know exactly when to begin and end the exposures of the photographs, for at present-day eclipses all important observations are made by photography. The impressions received by the eye are so fleeting, coming to the observer when he is not in his usual calm, calculating mood, but aroused by excitement and novelty, so that it would be no wonder if in the past mistakes have been made in interpreting the celestial phenomenon. At present-day eclipses, with the aid of the photographic plate, the astronomer devotes his attention to getting a good series of photographs, and after the few minutes of the eclipse are over the plates can be developed and permanent records obtained which can be studied at leisure through weeks, months and perhaps years. When the Spaniards had quieted down, after their first outburst, all that was heard in the eclipse camp was the steady count of the observer calling out the seconds as they passed, the quiet words of the observers giving commands to their assistants and the click, click of the apparatus as exposures were made and plate holders moved. Everything passed off without a hitch, and with the first reappearance of the sun our work was over and we could take a long breath.
We had been favored with clear skies, how many others were equally fortunate? It did not take us long to find out, for the Spanish government had installed right in our camp a telegraph office, and for fifteen days no less than three operators were at our service to send and receive our messages; and for this not a single cent of money was asked or expected. It was found that fifty miles to the west of us, at Albania, where were the observers from the Lick Observatory under Professor Campbell, there were thin clouds, while one hundred miles to the east along the Mediterranean coast the Englishmen were even more unfortunate in having the clouds denser. In the northeastern part of Spain at Burgos more astronomers were located than at any one place, and here too was King Alfonso of Spain. Five minutes before totality it was pouring rain there, but as if by a miracle a little blue patch of sky appeared, and the eclipse was seen under perfect conditions. The weather along the eclipse track was: in Labrador, cloudy, no observations made; in Spain, cloudy and clear; in the islands of the Mediterranean, cloudy; on the coast of Africa, slightly cloudy; but further inland and along the rest of the eclipse track the skies were perfect. All three parties of the Naval Observatory were fortunate in having their work unhindered by a single cloud.
My own work was entirely spectroscopic. The photographic plates were developed within the walls of the college of Daroca, and in the long hours necessary for this work I was greatly encouraged and assisted by my good friend the rector of the college, Padre Felix Alvirez. Daily intercourse with this reverend father endeared him to me very much, and Srs. Lorente, Soria and Padre Felix made my stay in Daroca one of the most interesting spots of my whole life by the kindness with which they bore my imperfect Spanish, by the interesting bits of history they told of Daroca and by the deep insight each gave of the courtesy of a Spanish gentleman's heart.
The developed plates show that a great amount of detail had been caught, on one plate there being no less than twenty-five hundred lines all in good focus. A careful and accurate measurement made of the position of these lines of the spectrum will give much of scientific interest about the constitution of the sun's atmosphere.
As a result of the observations of this latest eclipse much valuable information will undoubtedly be gained about the sun and its immediate surroundings. These discoveries, however, will all be in minor details, and it is hardly probable there will be any wonderful or startling revelations made.
It is a long time till the next eclipse to be generally observed in 1912, and astronomers will have plenty of time to fully investigate their photographs of this past summer.
The instruments that took weeks to mount and adjust were easily pulled apart and packed, and in a few days after the eclipse everything was in readiness to be transshipped home.
The writer left Spain with many regrets, and with many happy recollections of a pleasant and profitable time spent among the courtly Spaniards.