Page:Popular Astronomy - Airy - 1881.djvu/20

 6 path, becoming more and more horizontal, till it reaches a certain height in the south, where its course is exactly horizontal; and then it declines by similar degrees, and sets at a place in the west, just as far from the north point as the place where it rose in the east, If you select a star that has risen near to the north, it takes a long time in rising to its greatest height, it rises to a higher place in the south, and sets by the same degrees. Lastly, if you look to the north, and give your attention to those stars which are fairly above the horizon, you find the stars going round and describing a complete circle: these stars are called circumpolar.

Here I would remind my auditors that it is necessary, in order to understand a Lecture upon Astronomy, that they should have a little previous knowledge of the science that they should know the names and situations of some of the more conspicuous stars, otherwise it will be impossible for them to proceed. I therefore assume that a portion of my audience possess this requisite knowledge. I presume you know which is the Polar Star; I presume also that you know which is the Great Bear. Now, these are objects of such importance, that nobody ought to think of entering an astronomical lecture-room who is not acquainted with them. There is another star remarkable for its brilliancy, which is in this country circumpolar, called Capella; and there is another star, which is also nearly circumpolar, it is the bright star in the constellation Lyra.

Now I will call your attention to each of these in succession, The Polar Star is one which, roughly speaking, does not change its place during the whole night. Whenever you look out you find it in the same place. But speaking a little more accurately,