Cassie was taking two of her grandsons on their very first train
ride from Dayton, Ohio to Washington, DC.

A vendor came down the corridor selling Pop Rocks, something
neither had ever seen before. Cassie bought each one a bag.

The first one eagerly tore open the bag and popped one into his
mouth just as the train went into a tunnel. When the train
emerged from the tunnel, he looked across to his brother and
said: "I wouldn't eat that if I were you."

"Why not?" replied the curious brother

"I took one bite and went blind for half a minute."