Before night they came to a small stream, which was an admirable camping spot, and the yaks fairly reveled in the sweet, fresh water. There was no hesitancy in building a fire for the evening meal, and the hunting bags showed a good supply of game. That evening sitting under the great southern dome, with its glittering stars, the Professor had a most attentive audience when the various questions were brought up for discussion.
To those who are fairly observant, the heavens in southern latitudes cannot fail to attract attention because of the different arrangement of the stars. People living in the northern hemisphere have never seen the southern cross, nor the great fixed stars, Canopus or Achernar; and those below the equator have never viewed the polar star, and do not know the beauty of the brilliant star Vega.
The most intent listener, on all occasions of this kind, was George. "Tell us, Professor, how the mariner knows the direction of the south pole when there is no south polar star to show him?"
"Practically the same method is used as in the northern hemisphere. The north polar star does not in itself indicate which is north, but it is one of the points used in connection with another star which points out the direction.
"In the northern hemisphere there is a star called Alpheratz and another called Zaph, which are in direct line with the polar star. The two first stars named are exactly on what is called the equinoctial line. But the southern hemisphere of the heavens does not have a polar star to indicate the south, so that if you will now look directly above us you will notice two very bright stars. One of them is the fixed star Sirius, the most brilliant in the heavens; the other is Canopus, and a line along these two stars would go around the celestial sphere and point to the poles."
"But suppose we should be on the sea, and would not have anything else to guide us, what would there be to show which way is north and which direction south?"
"Sirius is easily distinguished, because it is, apparently, the largest of all the fixed stars. It cannot be mistaken. By taking that as a starting point, and following with the eye along past Canopus, you will be looking to the south pole."
"Isn't Sirius called the Dog Star? And hasn't it some connection with the dog days?"
"Yes; in the remote ages of the world, when every man was his own astronomer, the rising and setting of this star was watched with deep solicitude. The astronomers of Egypt determined the length of the year by the number of its risings. It foretold to them the rising of the Nile, which they called Siris, and admonished them when to sow. At that season of the year Sirius rises with the sun, and owing to its intense brilliancy, the ancients supposed that it blended its heat with the sun and thus was the cause of the intense heat; hence during that time were called dog days. At present what are so designated are the days between the 3d of July to the 11th of August."