Three engineers boarded a crowded bus and somehow managed to work their way to the middle of the vehicle where they found three girls willing to exchange their seats for a place on the guys' laps. After travelling like that for several minutes, the first girl asked the man on whose lap she was perched: "Are you by any chance an electrical engineer?" "Yes, I am," he replied, surprised. "How did you know?" "Easy," she said cheekily. "I'm getting shocked by your soldering iron." A few minutes later, the second girl asked her guy: "Do you happen to be a mechanical engineer?" "Why yes," he said. "How did you know that?" "Simple," she smiled. "Your piston is scraping my cylinder." Shortly afterwards, the third girl turned to her guy and asked: "Are you a civil engineer?" "I certainly am," he answered. "How could you have known that?" "Well," she said, "I figured it out as soon as your dam burst and flooded my village."