Hydra, the Water-snake, first rears a venomous head above the eastern horizon on January 5th about 9 P. M. He slowly squirms along the southern horizon, his length being so appalling that it takes him four months to completely pass any one point in the sky.
Along the body of this Water-snake are scattered a few 4th magnitude stars. The twinkling lights of these stars may be followed far to the south and then east, almost to the boundary of Scorpio. Indeed, when the Watersnake is completely above the horizon, as he is in April, these stars show that his long length stretches over nearly a quarter of the sky! Some poets state that this creature had one hundred heads, others claim that he had only nine. However this may be, there is only one that is easily traced and this lies, triangle-shaped, just below Leo, the Lion.
The only noticeably bright marking on the Water-snake is the orange-hued star of the second magnitude which lies upon the reptile's heart. This star is called Cor Hydræ after its location, but it also has the name of Alphard, the Solitary. Since the naming of the star, science has discovered the latter name to be rather a misnomer for it has a telescopic companion of a pale shade of green. Cor Hydræ rises in the early evening on the 21st of February, and passes the meridian about 9 o'clock during the middle of March.
The northernmost star of the group that marks the head is also a double. This double consists of two stars of the 4th and 8th magnitudes, the larger one being yellow and the smaller purple.
Double Stars on Hydra, the Water-snake.
Two geometrical figures called Corvus, the Crow, and Crater, the Cup, rest on the back of this Lernean Hydra. These two small constellations are easily traced, one having the form of a quadrilateral figure and the other a section of a circle. Kippax says that Crater has been variously called the Cup of Hercules, the Cup of Achilles, the Cup of Medea and the Wine Cup of Noah. The Greeks called Crater the "Goblet of Apollo" but according to Manilius it was the "generous Bowl of Bacchus," God of Wine.