Popular Science Monthly/Volume 45/October 1894/Astronomy of the Incas


THE traveler who in these days penetrates to the high plateaus of upper Peru and Bolivia, explores the basin of Lake Titicaca, and returns to Cuzco, is struck with the great number of ruins, hieroglyphic inscriptions, broken pottery work, and huacas which he meets at every step. They are the relics of the fanaticism of the conquerors and of their unbounded rapacity. Of the magnificent palaces adorned with gold and silver, the temples of the sun glistening with jewels, and the astronomical columns which stood at all points in the country from La Paz to Anito, there remain nothing but fragments of crumbled walls, an infinite number of pieces of bricks, deformed and mutilated statues disintegrated by time, blocks of granite and basalt standing in the deserted fertile lands like black ghosts, and at long distances apart a few tombs which have been forgotten by the Spaniards. The monuments standing at Tyahuanaco and on steep hills difficult of access, and in the archipelagoes of Lake Titicaca, although dilapidated and also victims of the hands of iconoclasts, deserve serious attention on account of their relatively good state of preservation.

Popular superstition has, furthermore, contributed no little to preserve the ruins of Lake Titicaca from complete spoliation.

Why are not more pains taken to send out scientific expeditions to these regions, to study the ancient civilization of the Incas? A work might be undertaken there of like nature with that which has been accomplished in Egypt by Champollion and Mariette Bey. Much that is valuable has been done there, it is true; but the whole story is still far from being told, and I am confident that huacas have many secrets and surprises in reserve for us. The astronomy of the Incas, a curious side of Peruvian civilization, while it has been lightly touched upon by some of the American reviewers and superficially noticed by a few explorers, is yet almost wholly unknown to us. Some even, of whom Mr. Wiener is one, have gone so far as to deny that astronomy existed among these peoples, or to reduce it to simple rudimentary notions. Yet we have only to keep our eyes open in passing through the country, or to consult the contemporary annals of the conquest, to be assured that their science was not a mere chimera or a legend invented to amuse. It would be strange, indeed, if a people whose only cult was the worship of the stars had not been moved to study the nature, movements, and phenomena of the heavenly bodies, and had not attempted to explain them in some way.

The proofs that the Incas. . . had a real system of astronomy are scattered, partly in what remains of the monuments that were consecrated to the sun, and partly in the accounts of historians—accounts which, whether because their importance has not been suspected, or because of the difficulty of quoting them, most of them having been printed only once, others having remained in the state of manuscript, and very few of them having been translated, are but little known to men of science. Whatever the verity of the legends preserved in these accounts, we find a comparatively highly developed astronomical system among the Incas, of which the most interesting parts are here given from rare documents already published, and from American manuscripts and traditions. The work has not before been done so completely.

Six nations only—China, Mongolia, India, Chaldea, Egypt, and Australia—had, before the discovery of America, divided the visible celestial sphere into constellations, and had used figures of their own invention to represent them. The Peruvians, although situated at the meeting of the Northern and Southern hemispheres, did not extend their division over the whole sphere; they recognized and studied only a few of the more brilliant constellations, like the Pleiades, the Jaguar, the Standard, the Southern Cross, and some other groups which have not yet been identified.[1] It is probable that they extended this division further than the first historians—who were not learned in astronomy, and could therefore pay little attention to all the details—represent. Later writers speak of other constellations which they do not mention. The Incas called the milky way the dust of stars, and gave names to its different parts. What is now called the Coal Sack was figured by them as a doe suckling her fawn—a simple and poetic transformation of the Grecian and Aryan legend of Hercules and his nurse.[2] A few stars of the first magnitude, such as Capella and Vega, had special names.[3] It is almost impossible that the Incas should have failed to give distinct names to the splendid stars of the Southern hemisphere, such as Sirius, Canopus, Achernar, etc. The silence of historians respecting this point is far from being conclusive, and may be accounted for by supposing that many of these stars not being visible in our hemisphere, they did not ask the natives for their names, and limited their inquiries to the stars of the Northern hemisphere which they knew.

The only planet which the Incas had discovered was Venus, which they called the hairy, on account of the brightness of its rays. They said that, being the most brilliant of the stars, the sun would not permit it to be separated from him, and obliged it to attend his rising as well as his going down, just as at the courts of kings only the most distinguished lords and the handsomest ladies were admitted to the ceremonious royal risings and retirings. It appears nearly certain that the Incas spoke of Venus under two different names, according as it preceded or followed the sun. To this day the native Peruvians name it, in fanciful language, the eight-hour torch and the twilight lamp. As this star served to show the Indians when it was time to prepare the maize for cooking, they also gave it a name indicative of that act. A chapel in the Temple of the Sun was consecrated to this planet.

The phases of the moon were well known to the people, and they attributed life and movement to it. When the moon was invisible, during the days preceding the first quarter, they said it was dead, and would rest three days in the tomb, beyond the snowy mountains and the immense ocean. Then it would rise again, to their great joy. To the people of Asia and North America the spots on the moon represented a rodent—a hare or rabbit—or a human being. The Incas perceived in it a young woman, and said that once upon a time the daughter of the king, walking in the light of the moon in one of those limpid and blue nights peculiar to the tropics and to these latitudes, suddenly fell in love with the star of the night. Desiring to possess him, she went and hid herself in the top of a mountain by which he would pass, sprang upon him at a favorable moment, and became one body with him.[4] The moon, called by names which signified sister or wife, was regarded as the first wife of the sun, and was represented by a silver plate bearing a woman's face. It, too, had its sanctuary, occupying a station of honor in the temple of the supreme god.

The difference between the seasons not being distinctly marked in Peru by variations either in moisture or temperature, it was important to make very careful observations in order to determine the times for planting and harvest. The only method was by experiment. The attention of the ancient Peruvians was particularly directed to the time when the sun passed the zenith, for then it cast no shadow at noon. They also observed it very carefully at the June solstice when it was seen nearest to the horizon; and they succeeded, as we shall see, in giving their observations scientific precision.[5] The solar spots had also been observed.

In explanation of the circular motion of the sun, the Incas said that it was hung in space by a cord; that it entered the sea in the evening, passed under the earth, and reappeared twelve hours afterward in the opposite part of the horizon.

The god himself was represented in sculpture, according to M. Wiener, in statues of gold or reddish-brown porphyry, with "his forehead encircled by the royal fillet in the midst of four fabulous animals moving around him." The same author, on the evidence of some monuments resembling the menhirs of the Druids, gives another explanation of the circular motion of the sun. "It is regarded," he says, "as a being which comes to rest at night after its daily march, in the inaccessible inclosure of the sanctuary (called by a Quichua term signifying the place to which the sun is attached). The holy object consists of two granite blocks about a metre in height, on the inner faces of which have been found holes about fifteen centimetres deep and nine centimetres in diameter." This was narrow quarters for a star as voluminous as the sun! We shall find further on that M. Wiener gives the same name to a system of observatories. The illustrious Peruvianologist has confused this word with the identical one which represents the year in the Quichua language.

The earth was believed to be flat and circular, and the center of it was shown in the sanctuary of Cuzco, the name of which, according to Garcilaso, signifies umbilicus, or navel. The Greeks had a similar belief, and located the center of the earth in the Temple of Apollo, another solar deity, at Delphi, which they called ΟμΦαλος, the navel of the inhabited world. It is celebrated under that title in some of the Pythian odes of Pindar. The earth, the Indian name of which signified "everywhere," was the only one of the stars that had no sanctuary in the Temple of the Sun. Like the peoples of the Aryan race, the Incas did not suspect that it was endowed with motion. Only the revolution of the stars existed to them; and the earth, instead of being a planet suspended in space, gravitating round the sun, and turning upon itself, was supposed to be fixed in the midst of a moving celestial sphere.

When the moon was eclipsed the Incas supposed that it was ill, and uneasiness prevailed whenever it appeared obscured. If the eclipse was total, they supposed that the star was perhaps dead, and that, not being capable of maintaining itself in space, it would fall to the earth, crushing the poor mortals thereon and that the world would come to an end. For this reason when an eclipse of the moon was beginning—an event they were not able to predict—the Incas with such instruments as were within their reach—drums, trumpets, cymbals, etc.—made a frightful noise, and, tying up their dogs, tormented them so as to extort the most hideous cries from them, in the hope that the moon, being a friend of dogs, would be softened by their howling and try to return to life. Men, women, and children joined with their princes in conjurations to avert the catastrophe. As long as the eclipse continued they kept exclaiming, "Mama-quilla, Mama-quilla!" which might be paraphrased, "God save us!" and they supplicated the sun to aid them. After the eclipse had passed away they sang in chorus the praises of the god Pachacamac, who had cured the pale star of night. Garcilaso adds to this story that these practices were all still in vogue in his time—that is, a half century after the conquest.

Mention is made in the Memoirs of Garcilaso of a comet which appeared at the time of the death of the Inca Huascas, and of another which was visible some time afterward, while Atahualpa was a prisoner of the Pizarros. These apparitions were regarded as annunciations of imminent woe. So, likewise, were shooting stars, of which an extraordinary fall took place during the reign of the same Inca.[6] Montesinos speaks of the appearance of two comets during the reign of Yupanqui—one had the form of a lion, the other of a serpent. "The sun," he wrote, "had sent these two animals to destroy the moon. So the Indians directed a hailstorm of stones at the lion and serpent to veil their light and prevent them from tearing the moon to pieces, for if they succeeded in carrying out their purpose everything on the earth would be changed into savage and hideous beasts, women's hair into vipers, and other things into bears, tigers, and similar evil creatures." The Indians still believe that the shooting stars drop from the sky, and utter prayers for deliverance when they see them.

The Inca year was originally divided into twelve lunations, each of which had its special name. But experience having shown that this lunar year was ten or twelve days shorter than the solar year, a reform was determined upon. Montesinos asserts that an assembly of amantas in the reign of Agay Manco thoroughly rearranged the calendar, dividing the year into three months of thirty days each, and the month into three weeks of ten days each, and adding to complete the solar year a half week of five days, which was made six days every fourth year. The Inca Yahnar Huquiz, grand astronomer, soon discovered that an error of one day would appear after four hundred years in the calendar thus instituted! The Indians reckoned time by this system till the Spaniards came.[7] Garcilaso says that the Inca Tapac Yupunpuy discovered, three centuries before the conquest, that the period between the solstices was three hundred and sixty-five days and a quarter, and that he caused the intercalation of ten days and a quarter, distributed among the lunations, in order to make the lunar and solar years agree. Is it not strange to see the Gregorian calendar invented and applied by the Incas three hundred years in advance of the Europeans? The year was called by a name derived from a Quichua word signifying to bind, and the half century of fifty years was figured by the hieroglyph of a bundle of reeds tied with a ribbon. Each of the twelve months was named after its principal festival.

In the month of December a peculiar dance, in which only men participated, was performed with great solemnity on the plaza in front of the Temple of the Sun at Cuzco. Offerings were made to the divinity of lamas, which were burned on pyres of odorous woods; and birds and various animals, but rarely human victims, were sacrificed. The dances followed, representatives of all the provinces taking part in them. These dances were instituted by Huayna Capac, the twelfth Inca. Two or three hundred men, holding one another's hands, executed a kind of farandale, stepping in concert two paces forward and one backward, so that they constantly gained ground, and all the time singing of the exploits of the Incas. Huayna Capac had a golden chain made which they all took hold of. It was as long as the two plazas of Cuzco, and was composed of rings of the diameter of the sun. The Indians hid it carefully at the time of the arrival of the Spaniards, and a legend relates that it was thrown into the depths of Lake Titicaca. The young Incas appeared at this festival, according to the expression of the historian Balboa, as armed knights. The sages charged with their education prepared them for the solemnity by scourging them with leaves and rubbing their figures with the blood of the offered lamas. The blood of the lamas and other victims also flowed in January, February, March, and April. The feast of the corn harvest was celebrated in May, and was held in the Gardens of the Sun, on the hill Colcampata. The people intoxicated themselves with a fermented drink (chicha), made from corn and fruit, and danced in masquerade.

For the June festival, which was dedicated to the sun, rude statues of men and women were made and covered with rich vestments. The courts of the temples were strewn with flowers, and the reigning Inca, with the chiefs of the tribes, executed sacred dances. The feast of the Pleiades is still celebrated in this month. In July and August spotted lamas and pigs were sacrificed, as an offering to obtain abundant crops.

The vernal equinox was celebrated in September. All the idols were collected in one place previous to the rising of the moon. As soon as the star appeared above the horizon the Indians uttered loud cries for the aversion of harm, and struck one another with whips of burning straw; washed in a running brook; and, on their return, sacrificed a hundred white lamas. They kept intoxicated for four days, and ate cakes prepared by maidens with the blood of the victims. Another hecatomb was offered in October, and in November the princely youth who were to be given arms in the next month had their ears pierced.[8]

These Peruvian ceremonials were very like those which Ovid has described. They were not the only ones; an edict of the Inca Pachacutec mentions three regular festivals occurring in each lunar month; there were also days for fairs and markets, and a rest day occurring every nine or ten days, like the nondines of the Romans, but not corresponding either with the quarters of the moon or the week, although the phases of the moon were well known to the Incas. As their lunar year fell behind the true time, they rectified their calendar constantly, trying to make it conform roughly with the phases of the moon.

The hours were not determinate spaces of time corresponding with a mathematical division of the day, but simple indications of such conditions as dawn, or morning, noon, sunset, and night.

The astronomical observations of the Incas were at first very elementary and empirical. They marked the day when the sun passed over the zenith. An experiment of the simplest character will be sufficient to account for the conclusions they drew from this observation. If we plant a stick vertically, and observe the shadow which it casts when shone upon by the sun, we shall find that at noon toward the end of December, this shadow is very long and directed toward the north; then it diminishes gradually till the day when it is shortest at noon. In the Southern hemisphere the shadow follows an inverse direction to this, and is longest at noon in June and shortest in December. The days when the shadow is longest, beyond the tropics, are the same for all places in the same hemisphere. But the days when there is no shadow at noon are not the same for all latitudes in the same hemisphere within the tropics. A day's difference exists for every forty kilometres. For this reason the Incas established observations at different distances from north to south, over the whole extent of their empire.

In order to verify the equinoxes, the amantas, or astronomers, arranged richly sculptured columns in the courts of the temples of the sun. On the approach of the equinox, they observed the shadow projected by the columns. These were placed in the center of a large circle through which a line, exactly oriented by experiment, ran from east to west. When they saw that the shadow struck this line in the middle, and that at noon the column was bathed with light on every side, they announced the equinoctial day. They then adorned the columns with flowers and fragrant herbs, and brought offerings of gold, silver, precious stones, and fruit to the god. The gnomon, or column, was surmounted by a throne of massive gold, in which the sun was to come and sit on that day, illuminating the tower on all sides.

The amantas perceived that only four moons passed when the shadow was turned toward the north, while there were eight moons when it was directed toward the south. They did not take into account that their observatories were situated between the equator and the tropic of Capricorn. But when the Incas had established their residence at Quito, their men of science immediately remarked that the two shadows were equal, and that the duration of their variations was exactly six moons. This is why the columns called equinoctial at Quito were especially venerated as the favorite abode of the great divinity.

Mr. Wiener mentions another astronomical apparatus which was intended for the precise verification of the time of the equinoxes: "A vertical well, dug mathematically in the line of the zenith, twice a year, in spring and autumn admitted the rays of the sun and gave light in its lowest depth to a vast tunnel over which it was bored. These observatories were called intihuatanas. These intihuatanas were doubtless real, but the assignment of such a purpose to them was a work of pure imagination." This apparatus, ingenious as it may have been, is too sensibly removed from historical tradition and from the study of the ruins of the solar temples to have really existed. It should further be remarked that such an observatory could be mathematically of service only for the September equinox.

In tracing the meridian the Incas appear to have limited themselves to raising a pillar perpendicular to the line which the shadow follows on the day when the sun passes the zenith, and that they reached this result by a series of trials. This accounts for the variations of a few minutes offered in the orientation of some of the monuments.

The Inca method of determining the solstices was very striking, and nothing like it is found with any other people. On this interesting point we can not do better than literally translate Garcilaso, a descendant of the Incas by his mother, who was better informed upon it than any other writer: "The common people counted the years by the crops, and all were acquainted with the summer and winter solstices. They have left conspicuously visible marks of them. There are eight towers which they constructed at the east, and eight others which they constructed at the west of the city af Cuzco, arranged in fours, of which two, smaller than the others and about three stories high, were placed between two others much larger. The other two towers were much higher than those which in Spain serve as lighthouses in the seaports and as observatories on the frontiers. These were intended for the astrologers, to give them a good view. The spaces between the smaller towers, being illuminated by the rising or setting sun, were for the solstices, and the towers on the east answered to those on the west, at the winter or at the summer solstice. In order to verify the event the Inca placed himself in a convenient spot, whence he watched whether the sun rose or set between the two small towers on the east and on the west, and thus the most skilled of the Indians found the astrology of their solstices.[9]

This description, equally naïve and unintelligible, requires some explanation. The towers and turrets went by fours, two large and two small, and there were two systems, intended for the observation, by one system of the winter solstice, by the other of the summer solstice. In position and relative distances they were so arranged that when the sun reached the tropic of Cancer the shadow cast by the northeastern turret was exactly tangential, at the moment of sunrise, to the southern face of the northwestern turret, and at the same time hid the sun from the amantas on observation in the corresponding tower; and vice versa at the moment of sunset. As the sky might be cloudy at sunrise, the astronomers posted to observe the setting sun replaced, confirmed, or rectified, when necessary, the determinations of the morning. The southern turrets were used in the system of observatories for the summer solstice.

Montesinos gives another version which seems different when taken literally, but substantially confirms the former. He relates that the Inca Capac Raymi assembled his learned men and astronomers to find the solstices. "There was a kind of solar quadrant formed by shadows, and with it they knew what day was long and what other was short, and at what time the sun went toward the tropics and returned from them. I saw four very ancient walls on a hill, and a son of the country affirmed to me that this building had served the ancient Indians as a clock." Though precise for that time and place, and quite original, no account has been taken in this method of the change in the obliquity of the ecliptic, forty-eight seconds a year, according to Delambre, the effect of which upon the azimuth is very sensible in those latitudes. Houzeau says that the Incas had no idea of this displacement; that they observed the June solstice only, and that the continued observations of the amantas proved the absence of a solar calendar. It is very possible that the Incas perceived that their observatory system finally became useless, and that, without stopping to inquire into the reason, they constructed new ones. There is no doubt that the Incas recognized the movement of the ecliptic some time before the other people of the Old World, but without comprehending it, without making the necessary deductions for it, and without including the important phenomenon in their calculations. Houzeau was mistaken in affirming that the Incas observed only one solstice. The historians are unanimous in describing a festival for each of them. We have seen, besides, that two systems of observatories existed, with towers and turrets in different positions, and consequently designed for the observation of two different solstices.

We need not, furthermore, presume that the people had no calendar, from the amantas observing the zenith passages of the sun every year. The day, hour, and minute of an eclipse are foretold now; yet astronomers are not prevented by this from studying the different phases of the phenomena.

The destruction of these observatories, which Garcilaso says were still standing in 1560, must be regretted. Those of Quito were destroyed by Sebastian Belalcazar, under pretext that they prompted the natives to idolatry. Only shapeless ruins of them are now to be found. The best preserved ones are at Cuzco, on the Carmenca hill. The question, long asked, whether the Incas used optical instruments, is now answered in the affirmative. Mr. David Forbes has brought from Peru a silver figurine, which represents a personage, probably an astronomer, holding to his eye a tube which is nothing else than a telescope. The figure is certainly of Peruvian origin, and dates from the period of the Incas.—Translated for The Popular Science Monthly from the Revue Scientifique.

In taking the recent census of India some difficulty was experienced, according to C. E. D. Black, in determining what should be regarded as a house. "The variety of structure was so great that a precise definition, such as satisfied census authorities in other parts of the world, became an impossibility in India. In the hill tracts one meets with collections of leaf-huts that are here to-day and gone to-morrow. Again, there is a portable arrangement of matting and bamboo that is slung on a donkey by the vagrant classes, though sometimes stationary on the outskirts of a village for months together. Then comes the more stable erection for the cultivator while engaged in watching his crops, and so on to the really permanent abode of the lower grades of village menials, with wattle and daub walls which last for years, and a roofing of thatch or palmyra leaves, renewed as necessary before each rainy season. In some parts of India a considerable space is walled in with a thick hedge of thorn or rattan, and the family expands in separate buildings as the sons marry, but all is considered to be a single 'house.' Pitched roofs, tiled or thatched, are usual in the moister tracts; flat-topped mud or brick buildings are almost universal in the dry plains of the Deccan and Upper India. Climate and the scarcity or plentifulness, as the case may be, are the main causes of the diversity of building; while social custom and the relative prevalence of the 'joint' or 'divided' family life among the Brahmanic classes often determine the interior construction and arrangement."
  1. Acosta, Histoire des Indes, 1591, Book V, chap. iv.
  2. Garcilaso, First Part of the Royal Commentaries, 1609, Book II, chap, xxiii.
  3. Acosta. Cælius, Cælum astronomico-poeticum, 1662, chap. xix.
  4. Garcilaso.
  5. Montesinos, Antiques Mémoires du Pérou, Book II, chap, ii, in manuscript at the Library of the Academy of History, Madrid.
  6. Garcilaso, Book I, chap, xxxiv.
  7. Montesinos, chapters xi and xii.
  8. Desjardins.
  9. Garcilaso, Book II, chap, xxiii.