Williams |
It has been necessary
to bear in mind these phases of practical civilization because much that
we know of the purely scientific attainments of the Egyptians is based
upon modern observation of their pyramids and temples. It was early observed,
for example, that the pyramids are obviously oriented as regards the direction
in which they face, in strict accordance with some astronomical principle.
Early in the nineteenth century the Frenchman Biot made interesting studies
in regard to this subject, and a hundred years later, in our own time,
Sir Joseph Norman Lockyer, following up the work of various intermediary
observers, has given the subject much attention, making it the central
theme of his work on The Dawn of Astronomy.[1] Lockyer's researches make
it clear that in the main the temples of Egypt were oriented with reference
to the point at which the sun rises on the day of the summer solstice.
The time of the solstice had peculiar interest for the Egyptians, because
it corresponded rather closely with the time of the rising of the Nile.
The floods of that river appear with very great regularity; the on-rushing
tide reaches the region of Heliopolis and Memphis almost precisely on the
day of the summer solstice. The time varies at different stages of the
river's course, but as the civilization of the early dynasties centred
at Memphis, observations made at this place had widest vogue.
Considering the all-essential character
of the Nile floods-without which civilization would be impossible in Egypt
- it is not strange that the time of their appearance should be taken as
marking the beginning of a new year. The fact that their coming coincides
with the solstice makes such a division of the calendar perfectly natural.
In point of fact, from the earliest periods of which records have come
down to us, the new year of the Egyptians dates from the summer solstice.
It is certain that from the earliest historical periods the Egyptians were
aware of the approximate length of the year. It would be strange were it
otherwise, considering the ease with which a record of days could be kept
from Nile flood to Nile flood, or from solstice to solstice. But this,
of course, applies only to an approximate count. There is some reason to
believe that in the earliest period the Egyptians made this count only
360 days. The fact that their year was divided into twelve months of thirty
days each lends color to this belief; but, in any event, the mistake was
discovered in due time and a partial remedy was applied through the interpolation
of a "little month" of five days between the end of the twelfth month and
the new year. This nearly but not quite remedied the matter. What it obviously
failed to do was to take account of that additional quarter of a day which
really rounds out the actual year.
It would have been a vastly convenient
thing for humanity had it chanced that the earth had so accommodated its
rotary motion with its speed of transit about the sun as to make its annual
flight in precisely 360 days. Twelve lunar months of thirty days each would
then have coincided exactly with the solar year, and most of the complexities
of the calendar, which have so puzzled historical students, would have
been avoided; but, on the other hand, perhaps this very simplicity would
have proved detrimental to astronomical science by preventing men from
searching the heavens as carefully as they have done. Be that as it may,
the complexity exists. The actual year of three hundred and sixty-five
and (about) one-quarter days cannot be divided evenly into months, and
some such expedient as the intercalation of days here and there is essential,
else the calendar will become absolutely out of harmony with the seasons.
In the case of the Egyptians, the attempt
at adjustment was made, as just noted, by the introduction of the five
days, constituting what the Egyptians themselves termed "the five days
over and above the year." These so-called epagomenal days were undoubtedly
introduced at a very early period. Maspero holds that they were in use
before the first Thinite dynasty, citing in evidence the fact that the
legend of Osiris explains these days as having been created by the god
Thot in order to permit Nuit to give birth to all her children; this expedient
being necessary to overcome a ban which had been pronounced against Nuit,
according to which she could not give birth to children on any day of the
year. But, of course, the five additional days do not suffice fully to
rectify the calendar. There remains the additional quarter of a day to
be accounted for. This, of course, amounts to a full day every fourth year.
We shall see that later Alexandrian science hit upon the expedient of adding
a day to every fourth year; an expedient which the Julian calendar adopted
and which still gives us our familiar leap-year. But, unfortunately, the
ancient Egyptian failed to recognize the need of this additional day, or
if he did recognize it he failed to act on his knowledge, and so it happened
that, starting somewhere back in the remote past with a new year's day
that coincided with the inundation of the Nile, there was a constantly
shifting maladjustment of calendar and seasons as time went on.
The Egyptian seasons, it should be explained,
were three in number: the season of the inundation, the season of the seed-time,
and the season of the harvest; each season being, of course, four months
in extent. Originally, as just mentioned, the season of the inundations
began and coincided with the actual time of inundation. The more precise
fixing of new year's day was accomplished through observation of the time
of the so-called heliacal rising of the dog-star, Sirius, which bore the
Egyptian name Sothis. It chances that, as viewed from about the region
of Heliopolis, the sun at the time of the summer solstice occupies an apparent
position in the heavens close to the dog-star. Now, as is well known, the
Egyptians, seeing divinity back of almost every phenomenon of nature, very
naturally paid particular reverence to so obviously influential a personage
as the sun-god. In particular they thought it fitting to do homage to him
just as he was starting out on his tour of Egypt in the morning; and that
they might know the precise moment of his coming, the Egyptian astronomer
priests, perched on the hill-tops near their temples, were wont to scan
the eastern horizon with reference to some star which had been observed
to precede the solar luminary. Of course the precession of the equinoxes,
due to that axial wobble in which our clumsy earth indulges, would change
the apparent position of the fixed stars in reference to the sun, so that
the same star could not do service as heliacal messenger indefinitely;
but, on the other hand, these changes are so slow that observations by
many generations of astronomers would be required to detect the shifting.
It is believed by Lockyer, though the evidence is not quite demonstrative,
that the astronomical observations of the Egyptians date back to a period
when Sothis, the dog-star, was not in close association with the sun on
the morning of the summer solstice. Yet, according to the calculations
of Biot, the heliacal rising of Sothis at the solstice was noted as early
as the year 3285 B.C., and it is certain that this star continued throughout
subsequent centuries to keep this position of peculiar prestige. Hence
it was that Sothis came to be associated with Isis, one of the most important
divinities of Egypt, and that the day in which Sothis was first visible
in the morning sky marked the beginning of the new year; that day coinciding,
as already noted, with the summer solstice and with the beginning of the
Nile flow.
But now for the difficulties introduced
by that unreckoned quarter of a day. Obviously with a calendar of 365 days
only, at the end of four years, the calendar year, or vague year, as the
Egyptians came to call it, had gained by one full day upon the actual solar
year - that is to say, the heliacal rising of Sothis, the dog- star, would
not occur on new year's day of the faulty calendar, but a day later. And
with each succeeding period of four years the day of heliacal rising, which
marked the true beginning of the year - and which still, of course, coincided
with the inundation - would have fallen another day behind the calendar.
In the course of 120 years an entire month would be lost; and in 480 years
so great would become the shifting that the seasons would be altogether
misplaced; the actual time of inundations corresponding with what the calendar
registered as the seed-time, and the actual seed-time in turn corresponding
with the harvest-time of the calendar.
At first thought this seems very awkward
and confusing, but in all probability the effects were by no means so much
so in actual practice. We need go no farther than to our own experience
to know that the names of seasons, as of months and days, come to have
in the minds of most of us a purely conventional significance. Few of us
stop to give a thought to the meaning of the words January, February, etc.,
except as they connote certain climatic conditions. If, then, our own calendar
were so defective that in the course of 120 years the month of February
had shifted back to occupy the position of the original January, the change
would have been so gradual, covering the period of two life-times or of
four or five average generations, that it might well escape general observation.
Each succeeding generation of Egyptians,
then, may not improbably have associated the names of the seasons with
the contemporary climatic conditions, troubling themselves little with
the thought that in an earlier age the climatic conditions for each period
of the calendar were quite different. We cannot well suppose, however,
that the astronomer priests were oblivious to the true state of things.
Upon them devolved the duty of predicting the time of the Nile flood; a
duty they were enabled to perform without difficulty through observation
of the rising of the solstitial sun and its Sothic messenger. To these
observers it must finally have been apparent that the shifting of the seasons
was at the rate of one day in four years; this known, it required no great
mathematical skill to compute that this shifting would finally effect a
complete circuit of the calendar, so that after (4 X 365 =) 1460 years
the first day of the calendar year would again coincide with the heliacal
rising of Sothis and with the coming of the Nile flood. In other words,
1461 vague years or Egyptian calendar years Of 365 days each correspond
to 1460 actual solar years of 365 1/4 days each. This period, measured
thus by the heliacal rising of Sothis, is spoken of as the Sothic cycle.
To us who are trained from childhood to
understand that the year consists of (approximately) 365 1/4 days, and
to know that the calendar may be regulated approximately by the introduction
of an extra day every fourth year, this recognition of the Sothic cycle
seems simple enough. Yet if the average man of us will reflect how little
he knows, of his own knowledge, of the exact length of the year, it will
soon become evident that the appreciation of the faults of the calendar
and the knowledge of its periodical adjustment constituted a relatively
high development of scientific knowledge on the part of the Egyptian astronomer.
It may be added that various efforts to reform the calendar were made by
the ancient Egyptians, but that they cannot be credited with a satisfactory
solution of the problem; for, of course, the Alexandrian scientists of
the Ptolemaic period (whose work we shall have occasion to review presently)
were not Egyptians in any proper sense of the word, but Greeks.
Since so much of the time of the astronomer
priests was devoted to observation of the heavenly bodies, it is not surprising
that they should have mapped out the apparent course of the moon and the
visible planets in their nightly tour of the heavens, and that they should
have divided the stars of the firmament into more or less arbitrary groups
or constellations. That they did so is evidenced by various sculptured
representations of constellations corresponding to signs of the zodiac
which still ornament the ceilings of various ancient temples. Unfortunately
the decorative sense, which was always predominant with the Egyptian sculptor,
led him to take various liberties with the distribution of figures in these
representations of the constellations, so that the inferences drawn from
them as to the exact map of the heavens as the Egyptians conceived it cannot
be fully relied upon. It appears, however, that the Egyptian astronomer
divided the zodiac into twenty-four decani, or constellations. The arbitrary
groupings of figures, with the aid of which these are delineated, bear
a close resemblance to the equally arbitrary outlines which we are still
accustomed to use for the same purpose. |
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