Read Ebook: Stonehenge and Other British Stone Monuments Astronomically Considered by Lockyer Norman Sir

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PAGE

PREFACE v

CHAPTER

APPENDICES.

INDEX 333

FIG. PAGE

STONEHENGE

INTRODUCTORY

In the book I published ten years ago, entitled "The Dawn of Astronomy," I gave a pretty full account of the principles and the methods of observation which enable us to trace the ideas which were in the minds of the ancient Egyptians when they set out the line of a temple they proposed to build.

Numerous references to the ceremonial of laying the foundation-stones of temples exist, and we learn from the works of Chabas, Brugsch, D?michen and others, that the foundation of an Egyptian temple was associated with a series of ceremonies which are repeatedly described with great minuteness. Amongst these ceremonies, one especially refers to the fixing of the temple-axis; it is called, technically, "the stretching of the cord," and is not only illustrated by inscriptions on the walls of the temples of Karnak, Denderah and Edfu--to mention the best-known cases--but is referred to elsewhere.

During the ceremony the king proceeded to the site where the temple was to be built, accompanied mythically by the goddess Sesheta, who is styled "the mistress of the laying of the foundation-stone."

Each was armed with a stake. The two stakes were connected by a cord. Next the cord was aligned towards the sun on some day of the year, or a star, as the case might be; when the alignment was perfect the two stakes were driven into the ground by means of a wooden mallet. One boundary wall parallel to the main axis of the temple was built along the line marked out by this stretched cord.

If the moment of the rising or setting of the sun or star were chosen, as we have every reason to believe was the case, seeing that all the early observations were made on the horizon, it is obvious that the light from the body towards which the temple was thus aligned would penetrate the axis of the temple from one end to the other in the original direction of the cord.

Dealing with the existing remains of Egyptian temples, it may be said that the most majestic among them was that of Amen-R? at Karnak, dedicated to the Sun-God, and oriented to catch the light of the sun setting at the summer solstice, the time of the year at which the all-important rise of the Nile began.

Although the sun is no longer worshipped in Egypt or Britain, sun-worship has not yet disappeared from the world. Professor Gowland has recently brought to notice a surviving form of sun-worship in Japan. I quote his statement:--

"There on the seashore at F?ta-mi-ga-ura the orientation of the shrine of adoration is given by two gigantic rocks which rise from the sea as natural pillars. The sun as it rises over the mountains of the distant shore is observed between them, and the customary prayers and offerings made in that direction .

"It is, too, specially worthy of note that the point from which the sun is revered is marked by a structure of the form of a trilithon, but made of wood, placed immediately behind the altar. This representative of the trilithon is of very remote date in Japan, and has been in use there from the earliest times in connection with the observances of the ancient Shint? cult in which the Sun-Goddess is the chief deity. One of its important uses, which still survives, was to indicate the direction of the position of some sacred place or object of veneration, in order that worshippers might make their prayers and oblations towards the proper quarter."

The table of offerings must also be noted.

In the book to which I have referred, I also endeavoured to show that a knowledge of even elementary astronomy may be of very great assistance to students of archaeology, history, folk-lore and all that learning which deals with man's first attempts to grasp the meaning and phenomena of the universe in which he found himself before any scientific methods were available to him; before he had any idea of the origins or the conditionings of the things around him.

It may be well, however, in the present book to restate the underlying astronomical principles in the briefest possible manner; and this is the more easily done because, in the absence of measuring instruments, the horizon was the only circle which the ancient peoples could employ effectively, and we need only therefore consider it.

Indeed, whether we regard the Rig-Veda or the Egyptian monuments from an astronomical point of view, we are struck by the fact that the early worship and all the early observations related to the horizon. This was true not only for the sun, but for all the stars which studded the general expanse of sky.

We have therefore chiefly to consider the relation of the horizon of any place to the apparent movements of celestial bodies at that place.

We now know that the earth rotates on its axis, but this idea was of course quite unknown to these early peoples. Since the earth rotates, with stars infinitely removed surrounding it on all sides, the apparent movements of the stars will depend very much upon the position we happen to occupy on the earth. An observer at the North Pole of the earth, for instance, would see the stars moving round in circles parallel to the horizon . No star could therefore either rise or set--one half of the heavens would be always visible above his horizon, and the other half invisible. An observer at the South Pole would of course see that half of the stars invisible to the observer at the northern one.

If the observer be on the equator, the movements of the stars will appear to be as indicated in this diagram --that is, all the stars will rise and set, and each star will be, in turn, twelve hours above the horizon, and the same time below it. But if we consider the position of an observer in a middle latitude, say at Stonehenge, we find that some stars will always be above the horizon, some always below--that is, they will neither rise nor set. All other stars will both rise and set, but some of them will be above the horizon for a long time and below for a short time, whereas others will be a very short time above the horizon and a long time below it, each star completing a circle in a day .

Wherever we are upon the earth we always imagine that we are on the top of it. The idea held by all the early peoples was that the surface of the earth near them was an extended plain: they imagined that the land that they knew and just the surrounding lands were really in the centre of the extended plain. Plato, for instance, was content to think the Mediterranean and Greece upon the top of a cube, and Anaximander placed the same region at the top of a cylinder.

We have next to deal with the astronomical relations of the horizon of any place, in connection with the observation of the sun and stars at the times of rising or setting, when of course they are on or near the horizon; and in order to bring this matter nearer to the ancient monuments, we will study this question for both Thebes and Stonehenge. We may take the latitude of Thebes as 25?, Stonehenge as 51?, and we will begin with Thebes.

To consider an observer on the Nile at Thebes and to adjust things properly we must rectify a celestial globe to the latitude of 25? N., or, in other words, incline the axis of the globe at that angle to the wooden horizon.

Since all the stars which pass between the North Pole and the horizon cannot set, all their apparent movements will take place above the horizon. All the stars between the horizon and the South Pole will never rise. Hence, stars within the distance of 25? from the North Pole will never set at Thebes, and those stars within 25? of the South Pole will never be visible there. At any place the latitude and the elevation of the pole are the same. It so happens that many of those places with which archaeologists have to do in studying the history of early peoples--Chaldaea, Egypt, Babylonia, &c.--are in low middle latitudes, therefore we have to deal with bodies in the skies which do set and bodies which do not, and the elevation of the pole is neither very great nor very small. But although in each different latitude the inclination of the equator to the horizon as well as the elevation of the pole will vary, there will be a strict relationship between the inclination of the equator at each place and the elevation of the pole. Except at the poles themselves the equator will cut the horizon due east and due west; therefore every celestial body to the north of the celestial equator which rises and sets will cut the horizon between the east and west point and the north point; those bodies which do not rise will of course not cut the horizon at all.

The stars near the equator, and the sun, in such a latitude as that of Thebes, will appear to rise or set at no very considerable angle from the vertical; but when we deal with stars very near to the north or south points of the horizon they will seem to skim along the horizon instead of rising directly.

We now pass on to Stonehenge. To represent the new condition the axis of the globe will now require to be inclined 51? to the horizon. The number of northern stars which do not set and of southern stars which do not rise will be much greater than at Thebes. The most northern and southern stars visible will in their movement hug the horizon more closely than was observed under the Thebes condition.

The sun, both at Thebes and Stonehenge, since it moves among the stars from 23?/?? N. to 23?/?? S. each year, will change its place of rising and setting at different times of the year.

Now it will at once be obvious that there must be a strict law connecting the position of a star with its place of rising or setting. Stars at the same distance from the celestial pole or equator will rise or set at the same point of the horizon, and if a star does not change its place in the heavens it will always rise or set in the same place.

The sun as it changes its position each day, in its swing N. and S. of the equator, will rise and set on any day in the same place as a star which permanently has the same distance from the equator as that temporarily occupied by the sun.

Then supposing the azimuth to be 39? in the N.E. quadrant, it is written N. 39? E. For the other quadrants we have N. 39? W., S. 39? E., and S. 39? W., respectively.

The following table gives the amplitudes of rising or setting of celestial bodies having declinations from 0? to 64?, at Thebes and Stonehenge respectively.

AMPLITUDES AT THEBES AND STONEHENGE.

"Baugeschichte des Dendera-Tempels." 1877.

"Archaeologia," vol. lviii.

THE ASTRONOMICAL DIVISIONS OF THE YEAR

It is next important to deal with the yearly path of the sun, with a view of studying the relation of the various points of the horizon occupied by the sun at different times in the year. In the very early observations that were made in Egypt, Chaldaea and elsewhere, when the sun was considered to be a god who every morning got into his boat and floated across space, there was no particular reason for considering the amplitude at which the boat left, or came to, shore. But a few centuries showed that this rising or setting of the sun in widely varying amplitudes at different times of the year at the same place obeyed a very definite law.

In its northward passage it reaches the highest point at our summer solstice, and then goes down again till it reaches its greatest southern declination, as it does in our winter. At both these points the sun appears to stand still in its north or south movement, and the Latin word solstice exactly expresses that idea. The change of declination brought about by these movements will affect the place of the sun's rising and setting; this is why the sun sets most to the north in summer and most to the south in winter. At the equinoxes the sun has always 0? Decl., so it rises and sets due east and west all over the world. But at the solstices it has its greatest declination of 23?/?? N. or S.; it will rise and set therefore furthest from the east and west points; how far, will depend upon the latitude of the place, as will have been gathered from the preceding table .

These solstices and their accompaniments are among the striking things in the natural world. In the winter solstice we have the depth of winter, in the summer solstice we have the height of summer, while at the equinoxes we have but transitional changes; in other words, while the solstices point out for us the conditions of greatest heat and greatest cold, the equinoxes point out for us those two times of the year at which the temperature conditions are very nearly equal, although of course in the one case we are saying good-bye to summer and in the other to winter.

Did the ancients know anything about these solstices and these equinoxes? Dealing with the monumental evidence in Egypt alone, the answer is absolutely overwhelming. Many thousand years ago the Egyptians were perfectly familiar with the solstices, and therefore with the yearly path of the sun.

This fundamental division of the sun's apparent revolution and course which define our year into four nearly equal parts may be indicated as in Fig. 5, the highest point reached by the sun in our northern hemisphere being represented at the top.

In order better to consider the problem as it was presented to the early astronomers who built observatories to mark these points, we may deal with the bearings of the points occupied by the sun on the horizon at the times indicated. These points are defined, as we have seen, by their "amplitude" or their distance in degrees from the E. or W. points of the horizon. In the diagram I represent the conditions of our chief British sun-temple, Stonehenge, in latitude 51? N. approximately.

Taking the astronomical facts regarding the solstices and equinoxes for the first year of the present century, we find--

Sun enters Aries, Spring equinox, March 21. ,, ,, Gemini, Summer solstice, June 21. ,, ,, Libra, Autumn equinox, September 23. ,, ,, Sagittarius, Winter solstice, December 23.

These points, then, are approximately ninety-one days apart .

In Fig. 6 I deal with the "amplitudes" at Stonehenge, that is, the angular distance along the horizon from the E. and W. points, at which the sunrise and sunset are seen at the solstices; at the equinoxes they are seen at the E. and W. points. But as these amplitudes vary with the latitude and therefore depend upon the place of observation, a more general treatment is possible if we deal with the declination of the sun itself, that is, its angular distance from the equator.

The maximum declination depends upon the obliquity of the ecliptic, that is, the angle between the plane of the ecliptic and that of the equator at the time of observation. When the Stonehenge Sarsen Stones were erected this angle was, as I shall show later on, 23? 54? 30?. Its mean value for the present year is 23? 27? 5?; it is decreasing very slowly.

It will be obvious from Fig. 6 that in temples built to observe the solstices or equinoxes, if they were open from end to end, looking in one direction we should see the sun rising at a solstice or equinox, and looking in the other we should see the sun setting at the opposite one. I shall show later on that this statement requires a slight modification.

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