Complex sentence: The signs of the zodiac are in anticlockwise order around the inner zodiac dial: the zodiac wheel rotates clockwise with the hour hand but slips forward slightly with each rotation, so that the hour hand slowly passes through each zodiac sign in the course of the year.
Split into simpler sentences: The signs of the zodiac are in anticlockwise order around the inner zodiac dial: the zodiac wheel rotates clockwise with the hour hand but very slightly faster. As a result the hour hand moves slowly anticlockwise relative to the zodiac, so that it passes through each sign in the course of the year.