Page:Popular Astronomy - Airy - 1881.djvu/19

 Rh study Astronomy may enter, and by which they may attain a general comprehension of the rules which will lead them from one step to another.

I shall now proceed with my subject.

We will consider what are the general phenomena of the motion of the stars which are to be observed on any fine night. I must observe in the first place, that I shall use the term east to denote the whole of the horizon extending from the north point, through the east point, to the south point; the term west to denote the whole of the horizon extending from the south point, through the west point, to the north. Now, if we look out on any fine night, the first general fact that we observe is this—by watching that eastern horizon from time to time, through the whole extent from north to south, we see stars are rising; and by watching that western horizon from time to time, through the whole extent from north to south, we see that stars are setting. By looking out at different times in the course of an evening, you will see these things as I have pointed out. The next general fact which you will observe is this—that the stars do not rise perpendicularly. They rise obliquely; and those which rise near to the south or near to the north rise very slantingly indeed. Those nearest to the east rise at a certain slope, which is different for every different place upon the earth. Those which set near to the north or near to the south set very slopingly; those which set nearest to the west set with a sharp incline. This is the case so far as regards merely the rising and setting of the stars. But if you trace the whole path of any one of these stars, it describes such a course as the following. It rises somewhere in the east, in the sloping direction I have described; it continues to rise with a