Today, as part of our “Tricks of the Trade” series, we’re at the Houston Livestock Show and Rodeo, where students put goats and lambs up for sale to the highest bidder. Here, livestock auctions generate a pile of philanthropic money for a Texas scholarship fund, and the bids go up and up and up. But first: Air travel is in a snarl today with a power outage at London’s Heathrow Airport.