Time for a new puzzle. Today we feature a bowl of freshly popped popcorn. Depending on how it is prepared and cooked, some consider popcorn to be a health food, while others caution against it for a variety of reasons. Although small quantities can be popped in a stove-top kettle or pot in a home kitchen, commercial sale of freshly popped popcorn employs specially designed popcorn machines. Such steam-driven popcorn machines that popped corn in oil were invented in Chicago, Illinois, by Charles Cretors in 1885. A very different method of popcorn-making can still be seen on the streets of China today. Sometimes called a "popcorn hammer" - a large cast-iron canister is filled with un-popped corn kernels, sealed with a heavy lid and slowly turned over a fire. When the pressure reaches a certain value all of the popcorn explodes at once and is poured into a sack prepared in advance.