Information from gamearchives.org:

Each player selects a piece and begins the game either on the "Start Here" space or the "Or Here" space. Players take turns spinning the indicator and moving up as many places as the indicator shows. Players play in turn trying to reach the UPPER SPACE first. A player must reach the UPPER SPACE by exact count in order to win. "When the clock strikes 1" that is to say, when a player spins a 1, instead of moving forward one space his piece is immediately dropped to one of the spaces marked "Start Here" and the players piece is obliged to climb again. The only time a 1 does not cause a piece to return to the start space is if the piece is 1 spot away from winning and a 1 would be required to win the game. Then the 1 spin does indeed win the game.