dragons have given rise to
a significant set of astronomical terms. The Dragon marked the poles of
both ecliptic and equator; the Watersnake marked the equator almost from
node to node; the Serpent marked the equator at one of the nodes. The
"Dragon's Head" and the "Dragon's Tail" therefore have been taken as
astronomical symbols of the ascending and descending nodes of the sun's
apparent path--the points where he seems to ascend above the equator in
the spring, and to descend below it again in the autumn.

The moon's orbit likewise intersects the apparent path of the sun in two
points, its two nodes; and the interval of time between its passage
through one of these nodes and its return to that same node again is
called a Draconic month, a month of the Dragon. The same symbols are
applied by analogy to the moon's nodes.

Indeed the "Dragon's Head," [symbol], is the general sign for the
ascending node of any orbit, whether of moon, planet or comet, and the
"Dragon's Tail," [symbol], for the descending node. We not only use
these signs in astronomical works to-day, but the latter sign frequently
occurs, figured exactly as we figure it now, on Babylonian boundary
stones 3000 years old.

But an eclipse either of the sun or of the moon can only take place when
the latter is near one of its two nodes--is in the "Dragon's Head" or in
the "Dragon's Tail." This relation might be briefly expressed by saying
that the Dragon--that is of the nodes--causes the eclipse. Hence the
numerous myths, found in so many nations, which relate how "a dragon
devours the sun (or moon)" at the time of an eclipse.

[Illustration: HYDRA AND THE NEIGHBOURING CONSTELLATIONS.]

The dragon of eclipse finds its way into Hindoo mythology in a form
which shows clearly that the myth arose from a misunderstanding of the
constellations. The equatorial Water-snake, stretching from one node
nearly to the other, has resting upon it, _Crater_, the Cup. Combining
this with the expression for the two nodes, the Hindu myth has taken
the following form. The gods churned the surface of the sea to make the
Amrita Cup, the cup of the water of life. "And while the gods were
drinking that nectar after which they had so much hankered, a Danava,
named Rahu, was drinking it in the guise of a god. And when the nectar
had only reached Rahu's throat, the sun and the moon discovered him, and
communicated the fact to the gods." Rahu's head was at once cut off,
but, as the n