See those four numbers? Those are the four beats. Four stresses, as we say in the meter business. Tetrameter. Four. “Tetra” is four. Like Tetris, that computer game where the squares come down relentlessly and overwhelm your mind with their crude geometry and make you peck at the arrow keys like some mindless experimental chicken and hurry and panic and finally you turn your computer off. And you sit there thinking, Why have I just spent an hour watching squares drop down a computer screen?