The circle of 5ths involves starting in the key of C and moving down by 5ths until you eventually get back to C. Moving down a 5th or up a 4th is the same thing. This is explained in more detail in the complimentary intervals section. You can play around with the following animation to see how the circle moves. Although the animation features the Treble clef, the number and names of the sharps and flats is the same for the Bass clef.