Hence, on the sky, the stars will be found about one-fourth of the way from the zenith towards the horizon: Castor will be seen immediately above Pollux.

Next, suppose that at one of the hours named the observer wishes to learn what stars are visible towards the west and north-west:--Turning the map until the portion of the circumference marked W ...

N.W.is lowermost, he sees that in the direction named the square of Pegasus lies not very high above the horizon, one diagonal of the square being vertical, the other nearly horizontal.

Above the square is Andromeda, to the right of which lies Cassiopeia, the stars [beta] and [epsilon] of this constellation lying directly towards the north-west, while the star [alpha] lies almost exactly midway between the zenith and the horizon.

Above Andromeda, a little towards the left, lies Perseus, Algol being almost exactly towards the west and one-third of the way from the zenith towards the horizon (because one-third of the way from the centre towards the circumference of the map).